Justin wrote:
Hello,
After locking myself out of my apartment yesterday, I managed to make
the problem worse by fiddling with a piece of plastic in the lock
which broke off and ended up being shoved pretty far into the back of
the key hole. I tried using some needles to get it out, but no dice.
Anyone have a reasonably cheap solution? Would injecting acetone
damage the mechanism in any way?

Do you have an air compressor? Try using a fine jet nozzle to blast air into the
key hole through edge of the hole that has the pins (The saw-like edge of the
key. If you are lucky, the air will blast in behind the plastic, and push it
out. If that doesn't work at first, try moving the air jet back and forth along
the key hole to move the plastic around until it loosens and comes out.