Algodoo

twist the circle clockwise
and it will pop off
free to use!
it dosent need the physics slider changed
because its floating
also set the circle to back to
see how i made it
grey:protector
red:falloff mechinism
blue:red remover
and touch up the shape for me because right now it is a screw
if it was a octagon it would be a nut
and if it it was a hexagon it would be a bolt
use in disassembly scenes if you would like
trust me it adds a 3d feel to dismantling things
just because twisting it clockwise will take it off
if you want it to be more realistic
then mirror the whole thing and make it so you have to turn it
counterclockwise