Ouch

[oldsmoboat]

Rebuilding my rear caliper for the first time.  The manual said to use a compressor to push the piston out.  I didn't want it shooting across the floor so I put my fingers in the caliper to slow it down.
 
After the initial shock I was able to push the piston back in with my trapped fingers.
Live and learn.

[Charlie747]

Rebuilding my rear caliper for the first time.  The manual said to use a compressor to push the piston out.  I didn't want it shooting across the floor so I put my fingers in the caliper to slow it down.
 
After the initial shock I was able to push the piston back in with my trapped fingers.
Live and learn.

  Oooo extreme pain................

[Leo]

I put a "C" clamp on it and slowly open the clamp as the air blows the piston out.  As soon as the edge clears the "O" ring, your good to go. 

Be careful with air and mechanicals, there is no control with air.   Some auto training courses have examples of mechanics who have lost fingers.

[Boomer]

<LOL>
Did you bleed? You always have to bleed when working on your bike.
Damned Vampire Motorcycles!

Me, I couldn't figure out why a float bowl wouldn't seat on the carbs.
Seated fine once I pulled the straw from the carb cleaner spray out of it. 
In my defence it is a clear straw and I was high as a kite on carb cleaner fumes.

[Toxz Qwaste]

I've learned my best lessons at the School of Hard Knocks. Once in a while I go back just to keep my credentials current. I was using an old black & decker (aluminum body, no safety switch) recip saw recently when I got my finger in between the blade holder and the chassis. 1/3 hp doesn't sound like much but it was enough to keep my degree in humility up to date. 
The bonus is my young son also got an advanced coarse in foul language.