This is a piston stop for chainsaw motors.  I made it for working on a Stihl MS250.  You insert it through the spark plug hole to the opposite edge of the cylinder and then rotate the engine so the piston clamps the block at the end of the stop against the top of the cylinder.  Then you can remove or reinstall a clutch or flywheel.

I printed this out of PLA+.  I oriented it with the bottom of the stop block flat on the build plate so the layers are being squeezed together when in use.  I used tree supports under the handle which worked well.  I used an object modifier to print the block at the end solid while leaving the handle with 25% infill.