This is interesting, none of the equipment we used in the mid-60’s to 70’s had any such safety measures…

Fail-safe - Wikipedia, the free encyclopedia

I suppose it was a means of determining how to affect injury, since we had never seen injuries using these devices on television or otherwise, why we never incurred any injury and I was operating a tiller without a failsafe at age 12.  My father made a thick metal blade and attached it to the back of the plow which kept it from digging itself into the ground while running.   He added several holes into it so it would be adjustable.   He also created one with a plow blade on it for making rows.  Katherine’s father had also invented some piece of farm equipment as well.