Draw right hand, palm down, across the neck in a "throat cutting" motion from left to right.
One of eleven standard hand signals adopted by the American Society of Agricultural and Biological Engineers (ASABE). This video is used for the National Safe Tractor and Machinery Operation Program (NSTMOP), www.NSTMOP.psu.edu, and in the AgSafety4U program.
More Agricultural safety videos can be found on eXtension's AgSafety4u Youtube channel: https://www.youtube.com/user/AgSafety4u/videos
