Holding something while they are cutting it?
I had to learn the hard way why you don't remove your left hand from the front handle without at least setting the brake. Let me tell you why I own chaps.
Clearing saplings, little stuff, 2-3" diameter with the Husky 36. I was slashing through them like a scythe, then I came to one that was growing against something I didn't want to cut. Instead of putting the saw down and moving the something out of the way, I just cut that tree slowly. So of course it sat down on the bar and pinched.
Now comes the really stupid part. With the saw idling, I quickly grabbed the tree with my left hand and pushed it back. So the saw drops free, and I'm holding it by the back handle, so it's swinging down towards my leg. Reflexively, I tightened my grip on the saw and tried to torque it up away from my leg.
Now I've got a death grip on the saw that's swinging towards my leg, and the chain is accelerating like mad, because the finger that's gripping the tightest has a throttle under it. I one handed the saw's descent to a halt about 2" from my knee, the engine probably turning 13,000 rpm. Then I set the brake, shut the saw off, and never started a saw again until my 10 layer Labonville chaps arrived. If that had been a slightly larger saw, like my PS-510, that one thoughtless act would have resulted in a lot of pain, blood loss, and hospital bills.