The hazard
Machines do not know the difference between the material and your hand. Moving parts can crush, cut, pull in or throw things faster than anyone can react. Guards are there because nobody can stay perfectly careful every minute of every shift. A missing or bypassed guard can turn a normal day into a serious injury.
The action
The point of operation is where the machine does its work on the material, such as cutting, pressing, shaping or bending. If it can injure you, it must be guarded, and the guard is there to keep every part of your body out of the danger zone while the machine cycles. Never remove, bypass, prop open or tape over a guard to save time. If a guard is missing or broken, do not run the machine, and tell your supervisor. (29 CFR 1910.212(a)(3)(ii))
ASK THE CREW
What is our procedure when a machine jams, and who is authorized to lock it out?
From the talk: Machine guarding. Read it in full, free, with the questions and the sign-in sheet.