Do you have an IBM ThinkPad laptop with a missing key on the keyboard? Not a problem, you can fix the keyboard without taking your laptop to a repair shop. It’s not even necessary to disassemble the laptop and replace the whole keyboard. If you have all the pieces from the fallen key, then the repair process shouldn’t take a lot of time. These instructions
The key pieces are small and it may be very challenging to put them together, so be patient and have plenty of light in the work area.
A single key assembly (including mounting hinges) will cost you about $5-$6 including shipping.
If you cannot find the right key but still want to fix the problem, then you’ll have to replace the whole keyboard. You’ll find keyboard replacement instructions in the IBM hardware and maintenance guide.
Finally, if you still cannot figure out how to install the missing key back on the keyboard or if you have another laptop brand, check out this instructions for fixing keyboard keys.