We make wooden puzzles and have some machines that have to be used carefully.
This is a jointer.
This picture shown below is the jointer knives. These knives rotate with a high speed, and level the timber surface. As you can imagine, this part is very dangerous therefore the jointer has a wing shaped part which is called a spring return cutter head guard. This guard can be rotated and is always being pushed on side of the wall of the jointer to cover the knives for safety.
However, this guard can be moved easily and there would be a chance to touch the knives. If it happened, that would cause serious injuries to the hand. Better safe than sorry!
Juno bought a magnetic tool named "Magswitch" and attached an aluminum angle on the side. Magswitch is a very useful tool, it can be attached easily.
The last picture is not a jointer, it's a table saw. Table saws are a very dangerous tool. I know several people who lost their fingers. Juno also arranged Magswitch for a table saw. He attached an aluminum angle in a different way.
The most important thing is to prevent touching the blades of machines. We human beings are geniuses to make mistakes, aren't we?