It depends on how the corner is broken or how much is broken off. If it is just cracked, it's relatively easy. If broken off, you will have to build up material to make a new corner. In general, you can try the following steps.
1. disassemble laptop to gain access to the inside of the corner.
2. Find out what kind of plastic it's made of. Usually this is stamped in somewhere inside the case.
3. Get plastic repair epoxy that is compatible with the material. 3M Bumper Repair epoxy (part 380) will stick to almost anything.
4. For a crack: apply epoxy from inside, force through the crack, place reinforcing mesh over crack from the inside, cover mesh with epoxy. Work fast: sets up in 6 minutes!
5. For a hole or broken off corner: do the above step but then place mesh over the outside of the case over the broken area and build up higher than the contour of the original corner. Allow to cure completely. Grind, file or sand off built up material down to contour of original corner. Paint new corner if you want to after spraying on a coat of plastic auto body paint adhesion promoter first (buy at Advance Auto, etc.)
Good luck!
lifehacker, October 2009
