10.0 Lab Safety and Safety Practices
10.1 Safe practices in home, class, lab and work
MULTIPLE CHOICE
1. What are the first safety precautions to follow before beginning the application of a pesticide? (10.1)
a. Read the label
b. Check the recommended uses
c. Have clean water for spills
d. All of the above
2.
a.
b.
c.
d.
After applying pesticides, you should ____. (10.1)
Shower immediately
Wash clothes separately
Wash protective gloves
All of the above
3.
a.
b.
c.
d.
The most important first aid practice is to ____. (10.1)
Clean up spills
Continue applying pesticides
Dilute the poison
Panic
4.
a.
b.
c.
d.
Chronic toxicity is a danger caused by chemicals that accumulate in ____. (10.1)
50 gallon drums
Building floors and walls
Bodies of animals
Fallen trees
TRUE/FALSE
5. It’s best to apply chemicals on a sunny, windy day. (10.1)
FALSE
6. For inhaled poisons, carry the victim immediately to fresh air. (10.1)
TRUE
7. The best way to eliminate problems associated with leftover chemicals is to mix only the amount
needed per job. (10.1)
TRUE
8. Working domesticated horses does not present a kicking hazard, making it unnecessary to always
remain outside of the kicking range of the horse. (10.1)
FALSE
9. After using chemicals, the best option is to always wash and dry the clothing worn. (10.1)
FALSE
Safe / Unsafe
Directions: Place a circle around the S if the statement is a Safe Practice or a U if the statement is Unsafe.
(10.1)
10. It is the responsibility of every student to learn to work in a safe manner.
S/U
11. The student must pay strict attention to his work to insure safety.
S/U
12. Non-interference with others is a good safety rule.
S/U
13. Common sense and good judgment will avoid most accidents.
S/U
14. Keep all guards and safety devices in place when ever using the machines.
S/U
15. It is the responsibility of each student to report only major injuries of himself or his fellow students to
the instructor in charge.
S/U
16. You should not talk to another student while he is operating a machine.
S/U
17. The safest way to operate a machine is to get the work ready and then have another student turn on
the machine.
S/U
18. When clean-up time is announced, hurry and get your work finished.
S/U
19. Safety glasses must be worn when doing work that causes chips, sparks, or splattering of materials.
S/U
20. Students should not touch electrical devices of any type when hands or feet are wet.
S/U
21. Students should not operate a machine without safety guards in place unless the instructor is in the
room.
S/U
22. All wrenches and other tools should be removed from a machine before the power is turned on.
S/U
23. Machines should be allowed to come to a full stop before adjustments are made.
S/U
24. Loose neckties, loose sleeves, loose aprons, etc.. must be secured or removed before operating a
machine.
S/U
25. All students not operating a machine should stay out of the machine area.
S/U
26. Stock should be forced into a machine a little faster than it will take it.
S/U
27. Best to use guards on all machines or do the work by hand.
S/U
28. Cleaning with gasoline is a good way of getting the dirt from the floor.
S/U
29. Inspect all Electrical cords and remove them from service if damage is found and report it to teacher.
S/U
30. Store all flammable material in the storeroom.
S/U
COMPLETION
31. Eight pieces of protective clothing are ____________________, ____________________,
____________________, ____________________, ____________________,
____________________, ____________________, ____________________. (10.1)
coveralls, aprons, shop coats, footwear, gloves, hardhats, masks and respirators, earmuffs, ear
plugs
32. A ____________________ is used to draw attention to large items such as machines, cabinets, and
floors. (10.1)
focal color
33. The three focal colors for the nationally accepted shop safety color coding system are
____________________, ____________________, ____________________. (10.1)
ivory, vista green, aluminum
34. ____________________ masks should be worn when sanding, painting, welding, mixing soil,
shoveling grain, or wherever small particles may be inhaled. (10.1)
Dust
35. The 5 to 20 feet _________________________ around cattle is allowed to keep the animal calm.
(10.1)
flight zone
36. When setting a chute for loading and unloading hogs, it should slope no more than
____________________ degrees. (10.1)
25
MATCHING
Match the following meaning with their color codes. (10.1)
___D___ 37. red
___C___ 38. orange
___B___ 39. yellow
___E___ 40. blue
___A___ 41. green
A. safety
B. caution
C. warning
D. danger
E. information
Match the activity with the appropriate eye gear. (10.1)
A. welding
___B___ 42. glasses and goggles
B. minimum eye protection—good for most activities
___C___ 43. single-piece and cup
goggles
C. working with chemicals, light, or possible flying objects
___A___ 44. shaded lenses
SHORT ANSWER
45. Before discharging a fire extinguisher, about how far should a firefighter be from the fire? (10.1)
between six and ten feet of the fire
46. What are the three components needed to produce a fire? (10.1)
fuel, heat, oxygen
47. Name five common fuels. (10.1)
gasoline, alcohol, methane, propane, kerosene
48. What should you do if a fire breaks out in your school? (10.1)
notify a teacher, keep everyone calm, set off fire alarm, call the fire department, clear the area
49. If an emergency injury results, what steps should you take? (10.1)
call for help, call for ambulance or police, do not move victim unnecessarily, talk to the victim,
treat for shock
50. Describe four safety precautions to follow when using chemicals. (10.1)
Any four of the following: (1) reading the label carefully, (2) checking the recommended uses,
(3) having clean water and detergents available to wash spills, (4) wearing protective clothing,
(5) using extra caution with concentrated chemicals, (6) applying only the amount needed for
the job, (7) mixing only what is needed, (8) guarding against inhalation or ingestion, (9)
considering weather conditions, and (10) storing and disposing of chemicals properly.
51. Explain what should be done in case of an accidental pesticide spill. (10.1)
When an accidental spill occurs, contaminated clothing should be removed and the area (or
entire body) washed with plenty of water and soap or detergent. A shower should be used than
a bathtub because continuous clean water helps dilute the chemical. Chemical burns should be
bandaged with loose, clean, soft cloth. Flush poisoned eyes for at least five minutes with clean
water. For inhaled poisons, immediately carry the victim to fresh air. Provide expert medical
attention as soon as possible.
52. Explain the importance of selecting the best pesticides. (10.1)
If chosen correctly, the pesticide will kill or control the pest, won’t injure the plant, and is the
least harmful to the environment.
53. How can the spread of disease sometimes be halted without chemicals? (10.1)
proper sanitation
54. What are the most critical parts of the body that you should protect? (10.1)
The most critical parts of the body to protect are the face and eyes.
55. What is the most versatile item of protective clothing? (10.1)
coveralls
56. What is the best footwear for using machinery? (10.1)
leather shoes
57. What is the color indication for a radioactive area?
A radioactive area is marked by black and yellow stripes.
58. What is the purpose of an eyewash station?
The purpose is to provide an immediate flood of water to the eyes in case of an accident
involving the eyes
59. List some precautions for the safe handling of cattle. (10.1)
(1) Avoid loud noises; (2) Avoid shadows and contrasting patterns; (3) Do not push cattle too
hard; (4) allow them to follow the natural herd leader.
60. Discuss precautions for entering a manure pit. (10.1)
(1) Monitor the oxygen level while the worker is in the pit; (2) Make sure the pit is well
ventilated; (3) Use safety lines; (4) Have a person available outside the pit with self-contained
breathing equipment and safety line for rescue purposes.
61. List and describe the types of fire extinguishers.
Class A—marked with a green triangle
Class B—marked with a red square
Class C—marked with a blue circle
Class D—marked with a yellow star
10.2 Careers working with Hazardous Bio Materieals
MULTIPLE CHOICE
62. Farm chemicals such as pesticides should be stored in places where ____. (10.2)
a. children cannot get to them
b. they will not freeze
c. there are no sewer or drainage lines
d. all of the above
63. Livestock workers are exposed to all the following atmospheric contaminations except ____. (10.2)
a. dust
b. pesticides
c. asbestos
d. toxic and asphyxiating gasses
64. In animal confinement buildings, workers should wear dust filters providing protection from particles
____ in diameter. (10.2)
a. 1.2 microns
b. 0.5 microns
c. 0.2 microns
d. 0.3 microns
65. In silos, fermentation produces ____. (10.2)
a. carbon dioxide
b. nitrogen dioxide
c. both a and b
d. neither a nor b
66. A simple precaution for food handlers to observe concerning pesticides is to: (10.2)
a. wash the food
b. freeze the food
c. can the food
d. bottle the food
67. A ____ is a material capable of producing a cancerous tumor. (10.2)
a. tumor
b. carcinogen
c. toxin
d. chemical
68. Which of the following is the most complete definition of Biohazards? (10.2)
a. The potential danger or harm from exposure to such an agent or condition
b. A natural hazard to humans or animals
c. A man made hazard to humans
d. A biological agent or condition that constitutes a hazard to man or his environment
69. What are some potential hazards found in the Agriculture Laboratory? (10.2)
a. Bacteria cultures
b. Needles, scalpels and sharps
c. Waste
d. All of the above
TRUE/FALSE
70. Agriculture is not considered to be among the more dangerous occupations in the United States.
(10.2)
FALSE
71. People 25 years old and younger, because of their lack of experience, and people older than 64,
because of their loss of agility, tend to get hurt more often on farms. (10.2)
TRUE
SHORT ANSWER
72. Discuss ways of preventing diseases in animals and preventing transmittal to humans. (10.2)
Cleanliness, vaccination, quarantine of sick animals, and avoiding exposure.
73. List examples of toxic gases found in livestock confinement buildings. (10.2)
ammonia, methane, hydrogen sulfide, and carbon monoxide
10.3 Value of safety to Employees
MULTIPLE CHOICE
74. What type of material is preferred for footwear for most workers because of its strength, durability,
safety, and comfort? (10.3)
a. lightweight vinyl
b. rubber
c. canvas
d. leather
75. Chemicals inhaled are absorbed through the ____. (10.3)
a. Liver
b. Heart
c. Kidneys
d. Lungs
76. Heat stress suffered by workers during hot weather is sometimes called ____. (10.3)
a. heat exhaustion
b. heat prostration
c. heatstroke
d. all of the above
77. When unloading grain from a storage bin, a worker can be in a dangerous situation within ____.
(10.3)
a. 10 to 15 seconds
b. 4 to 5 seconds
c. 60 to 90 seconds
d. 20 to 30 seconds
78. Infectious viruses can be transmitted by ____. (10.3)
a. skunks
b. raccoons
c. bats
d. all of the above
TRUE/FALSE
79. Most injuries in the workplace are a result of dysfunctional equipment and could not have been
avoided. (10.3)
FALSE
80. If you always take the proper safety precautions, insurance is not needed. (10.3)
FALSE
81. Law does not require farmers, as many other occupations, to provide a safe and healthy workplace for
employees. (10.3)
FALSE
MATCHING
Match the terms on toxicity with the correct definition below. (10.3)
___E___ 82. Measures pesticide poisoning after single exposure
___C___ 83. Measures acute oral and dermal toxicity
___D___ 84. Measured by LC50 values (lethal concentration)
___B___ 85. Amount necessary to cause death
___A___ 86. Measures pesticide poisoning after repeated exposure
COMPLETION
A. chronic toxicity
B. lethal dose.
C. LD50 (lethal dose) values
D. acute inhalation
E. acute toxicity
87. The prevention of fire goes hand-in-hand with _________________________ of equipment and
_________________________ of work areas. (10.3)
safe use, efficient management
88. ____________________ toxicity is the measure of how poisonous a pesticide is after a single
exposure. (10.3)
Acute
89. The method to measure oral and dermal toxicity is by _________________________. (10.3)
lethal dose
90. To create the fire triangle and produce fire, these three components are necessary:
____________________, ____________________, ____________________. (10.3)
fuel, heat, oxygen
91. Inhalation toxicity is measured in ______________________________. (10.3)
lethal concentration
92. An important factor on the damage of hearing due to noise is ____________________. (10.3)
noise duration
93. ______________________________ is a danger when chemicals accumulate in the body. (10.3)
Chronic toxicity
94. A worker should not enter a silo for ____________________ weeks after it has been filled. (10.3)
3
95. ____________________ are diseases and parasites that can be passed between humans and animals.
(10.3)
Zoonoses
96. Breathing large amounts of dust can cause _________________________ syndrome in workers.
(10.3)
toxic organic dust
TRUE/FALSE
97. Unloading grain from a storage bin can present dangers from dust, mold, and trap hazards. (10.3)
TRUE
98. Fires do not present a serious hazard on livestock farms, and there is little need for elaborate
preparations for them. (10.3)
FALSE
SHORT ANSWER
99. Explain why loading and unloading livestock are particularly dangerous. (10.3)
Because the animals are excited and confused by what is happening.
100.
What are the three main routes by which poisons enter the body? (10.3)
Oral, dermal, and inhalation
101.
Name the three ways poisons enter the body. (10.3)
oral (swallowing), dermal (by contact with the skin), inhalation (breathing)
102.
Name the four toxicity categories. (10.3)
Highly toxic (I), Moderately toxic (II), Slightly toxic (III), Relatively nontoxic (IV)
103.
What does WPS stand for? (10.3)
Worker Protection Standard
104.
What is CPR? (10.3)
Cardiopulmonary resuscitation is a first-aid technique to provide oxygen to the body and
circulate blood when breathing and heartbeat stops.
105.
List examples of personal protected equipment for livestock workers. (10.3)
Safety glasses, leather gloves, safety shoes, and respiratory protection.
106.
Discuss ways to avoid heatstroke in workers. (10.3)
(1) Provide lots of drinking fluids; (2) Take breaks; (3) Dress in lightweight cotton clothes; (4)
Avoid sugar drinks; (5) Eat lots of fruits and vegetables to replace electrolytes in the body.
10.4 Impact of safety compliance on business
MULTIPLE CHOICE
107. A reflective-type emblem consisting of an orange triangle with a red strip on each of the three
sides is a (10.4)
a. railroad crossing emblem
b. radioactive emblem
c. slow-moving vehicle emblem
d. truck crossing emblem
108.
How many items of information should be listed on a pesticide label? (10.4)
a. 16
b. 3
c. 8
d. 10
109.
The signal words and symbols describe acute ____ of the pesticide. (10.4)
a. sensitivity
b. compounds
c. usage
d. toxicity
110.
Class B fires are those burning ____. (10.4)
a. metals
b. electrical equipment
c. paints and solvents
d. paper and textiles
111.
Avoiding hazards in handling livestock involves ____. (10.4)
a. designing facilities where workers are not in small areas with animals
b. using tile floors
c. maintaining low lighting
d. all of the above
TRUE/FALSE
112. The Environmental Protection Agency requires that Material Data Safety Sheets be available for
all chemicals in the workplace. (10.4)
TRUE
113. The Occupational Health and Safety Act sets minimum standards for respirators. (10.4)
FALSE
114. Class A fires are those burning ordinary combustibles such as paper, wood, and textiles. (10.4)
TRUE
MATCHING
Match the following classes of fire to their materials. (10.4)
___D___ 115. combustible metals
___A___ 116. ordinary combustibles
___B___ 117. flammable liquids
___C___ 118. electrical equipment
A. Class A
B. Class B
C. Class C
D. Class D
Match the following color symbols on fire extinguishers to the class of fires they are used for. (10.4)
A. green triangle
___C___ 119. Class C
B. red square
___D___ 120. Class D
C. blue circle
___B___ 121. Class B
D. yellow star
___A___ 122. Class A
Directions: Match the following eight safety principles with the approved practices. (10.4)
123. 24. Safety is an Ethical
a. The fundamental belief that injuries are, by their
D
Responsibility
nature, preventable is a catalyst that encourages us
to prevent injuries.
124. 25. Safety is a Culture Not
b. The purpose of the workplace audit is to discover
G
a Program
and remedy the actual hazards of the site before
they can injure workers.
125. 26. Management is
c. Reducing workplace injuries and illnesses
F
Responsible
reduces the costs of workers' compensation, medical
expenses, potential government fines, and the
H
126. 27. Employees Must Be
Trained to Work Safely
E
127. 28. Safety is a Condition of
Employment
A
128. 29. All Injuries Are
Preventable
B
129. 30. Safety Programs Must
Be Site Specific with Recurring
Audits of the Workplace
130. and Prompt Corrective
Action
131. 31. Safety is Good Business
C
expenses of litigation.
d. It is our ethical responsibility to do what is
necessary to protect employees from death, injury,
and illness in the workplace.
e. The employer must exhaust every reasonable
means to lead, motivate, train, and provision
employees to maintain a safe workplace.
f. Management’s responsibility is to lead the safety
effort in a sustained and consistent way,
establishing safety goals, demanding accountability
for safety performance, and providing the resources
necessary for a safe workplace.
g. Every person in the organization, from the top
management of the corporation to the newest
employee, is responsible and accountable for
preventing injuries.
h. Effective training programs both teach and
motivate employees to be a productive part of the
safety culture.
COMPLETION
132. A ____________________ of all fire extinguishers should be made to ensure that they are
useable in an emergency. (10.4)
safety check
133. If the chemical is moderately toxic, the label says ____________________. (10.4)
WARNING
134. A fire involving burning electrical equipment is a _________________________. (10.4)
Class C Fire
135. The ______________________________ issues regulations designed to reduce health risks
associated with chemicals. (10.4)
Environmental Protection Agency
136. It is very important to keep materials in their _________________________. (10.4)
original containers
137. OSHA stands for ___________________________________. (10.4)
Occupational Safety and Health Act
138. Labels on ____________________ products may be a matter of life and death in the event of an
accident. (10.4)
Hazardous
139. Sources of wiring information for farmers can be obtained from
___________________________________. (10.4)
Agricultural Wiring Handbook
140. ____________________ is a fire burning combustible metals. (10.4)
Class D
SHORT ANSWER
141. List the types of fire classes. (10.4)
Class A, Class B, Class C, Class D
142. Explain why a standby source of electrical power is recommended for modern livestock farms.
(10.4)
Emergency power sources are important because they can be lifesaving in some situations; for
example, if a fan fails in a manure pit, it could result in toxic gas buildup.
143.
This law protects all who come in contact with agricultural chemicals. (10.4)
Worker Protection Standard
144.
Where should a fire extinguisher be hung in reference to the floor? (10.4)
not more than 3.5 to 5 feet off the floor
145.
What six things should be checked during a fire extinguisher inspection? (10.4)
extinguisher is in its place, no mechanical damage, check to make sure it is fully charged,
examine nozzle for obstruction, make certain it has not been tampered with, proper class
extinguisher is in proper area
146.
Where should pesticides be stored? (10.4)
in locked cabinets
147.
List the EPA’s four toxicity categories and explain the regulations of each. (10.4)
Toxicity I chemicals—areas treated with chemicals carrying a “Danger-Poison” signal word.
Toxicity II chemicals—areas treated with chemicals carrying a “Warning” label. Toxicity III
chemicals—areas treated with chemicals carrying a “Caution” label. Toxicity IV—areas treated
with pesticides carrying no warning on the label.
148.
What standard points appear on the label of pesticide containers? List eight. (10.4)
Name and address of manufacturer; trade name; active ingredients; type of pesticide; form of
substance; EPA registration number; storage and disposal precautions; hazard statement;
directions for use; net contents and worker protection procedures under the new WPS
regulations
149.
If a chemical is in the highly toxic category, what signal word is required on the label? (10.4)
Danger, skull and crossbones, and poison
150.
What precautions should you take to provide a safer work environment? (10.4)
read all safety precautions, keep moving parts properly shielded, use tools and equipment
skillfully, avoid areas where objects may fall
151.
Describe the information listed on a pesticide label. (10.4)
Instructions for correct application, storage, and disposal of the pesticide; summary of
information by the pesticide manufacturer; physical properties; common name and chemical
name
152.
When should an approved face shield be worn? (10.4)
An approved face shield should be worn when any of the following activities are involved:
where hot molten metal or solder is being prepared; when milling, turning, sawing, shaping,
grinding, sanding, cutting, or stamping is being done; and where heat treating, tempering, or
kiln firing is being done.
153.
List four good storage precautions for pesticides. (10.4)
Any four of the following: storage site separate from other equipment and facilities, building
not located on flood plain, building built to prevent any runoff or drainage into critical areas,
well ventilated, source of heat and water, fireproof, secure locking system, supplies well
marked, supplies stored for ease of handling and safety
10.5 Safety Precautions with Biotech
MUTIPLE CHOICE
154. What percent of ethanol is in the spray bottle?
A. 70%
B. 20%
C. 50%
D. 95%
155.
A.
B.
C.
D.
Contaminated cultures should be discarded in the following way:
Autoclave for 10 min at any temperature or pressure
Autoclave for 30 min at any temperature or pressure
Autoclave for 30 min at 121 Deg. C at any pressure
Autoclave for 30 min at 121 deg. C at 15 psi of pressure
156.
A.
B.
C.
D.
Biotechnology labs are very
dirty
dusty
clean
unsanitary
157.
A.
B.
C.
D.
Other than for cleaning tool, what is dish soap used for?
Makes hands smell good
Acts as a wetting agent
Sterilization
Seals petri dishes and test tubes
158.
Forceps are used to:
A.
B.
C.
D.
Cut plant material & string.
Rinse tools & plant specimens.
Move plant material
Sterilize tools
159.
A.
B.
C.
D.
What is one safety precaution while using the autoclave?
minimize the flow of air currents
treat materials and equipment so they are free of contaminants
use gloves when removing equipment
wash work area with 10% bleach solution
160.
A.
B.
C.
D.
10% bleach is:
9 parts bleach: 1 part water
1 part bleach: 9 part water
10 parts bleach: 1 part water
1 part bleach: 1 part water
161.
A.
B.
C.
D.
The function of sucrose is to:
kill bacteria
slow down growth
provide energy
freeze up
162.
A.
B.
C.
D.
At what temperature does the autoclave heat tools and equipment?
121 F
100 F
121 C
100 C
163.
A.
B.
C.
D.
Why is the equipment sterilized?
So the fumes don’t kill you
So it dies
So it grows
So it doesn’t contaminate the medium or plants
164.
A.
B.
C.
D.
What does an autoclave do?
Cuts plant material
Sterilize material and equipment under high pressure and temperature
Seals petri dishes
Provides a temporary lid for bottles
SHORT ANSWER
165. Name two safety precautions for testing of new products in biotechnology research and
development. (10.5)
Any two of the following: testing in laboratories, greenhouses, other enclosures, small scale,
remote places, carefully observed
166.
What is a precautionary statement and give two examples. (10.5)
A precautionary statement lists any known hazards to humans, animals, and the environment
on the label. It will also advise the user how to minimize any adverse effects caused by the
pesticide. Examples include two of the following: Hazards to Humans and Domestic Animals,
Statement of Practical Treatment, Environmental Hazards, and Physical and Chemical
Hazards
10.6 Safely Operate and maintain Equipment
MULTIPLE CHOICE
167. When using a sprayer to apply a pesticide, be sure to ____. (10.6)
a. Spray near a school
b. Calibrate the sprayer
c. Pour pesticides in the drain
d. Store remaining pesticides
168.
A vacuum system that is attached to shop equipment is called (10.6)
a. clean up system
b. automatic sweeper
c. dust collection system
d. machine drier
169.
Most fatal accidents on farms are caused by ____. (10.6)
a. livestock
b. machinery
c. bees and insects
d. falls
SHORT ANSWER
170. Describe the difference between noise intensity and noise duration. (10.6)
Noise intensity is the energy in the sound waves. Noise duration is the length of time a person is
exposed to a sound.
SAFE/UNSAFE
Mark the following statements "S" for those statements which designate safe practices and "U"
for those statements which are unsafe. This test must be passed with a 100% in order for you
to use this tool in this program. (10.6)
171.
S/U
It is always necessary to report accidents to your instructor.
172.
S/U
Horseplay in the Ag shop is ok if nobody gets hurt.
173.
S/U
It is a good practice to wear proper safety equipment before you begin to operate machinery.
174.
S/U
Safety glasses should be worn at all times in the shop.
175. You should engage in conversation with another student while he or she is operating a machine in
the shop.
S/U
176.
S/U
When you are finished with a tool, clean it and put it back where it belongs.
177.
S/U
If a machine or tool is broken, it is your responsibility to report it to the instructor immediately.
178.
S/U
It is always necessary to report accidents to the instructor.
179.
S/U
Taking shortcuts and showing off are good to do in the shop.
180.
S/U
Screwdrivers make for pretty good pry bars if a real pry bar is not available.
181.
S/U
It is important to develop safe work habits.
182.
S/U
Always check the work area for potential hazards before beginning work.
183.
S/U
It is always recommended to use the appropriate tool for the job.
184.
S/U
It is not necessary that equipment be in good working order or adjusted properly.
185.
S/U
In case of electrical shock, make sure the electricity is off before beginning treatment.
186.
S/U
The student must pay strict attention to his work to insure safety.
187.
S/U
Duct tape works well on broken tools in order to keep them in operating condition.
188.
S/U
189.
S/U
When using a handsaw, it is a good idea to secure the board you are cutting with your knee.
Never smack the heads of 2 hammers together.