If you come across a very damaged screw-head - or a very stubborn screw, first start with the WD40,putting a spray of it around the screw and under the head. Make sure to let it work for a few minutes, then wipe away as much as you can - soyour tool can get good purchase.

High-Torque electric screwdrivers can sometimes take screws out with ease that you had no hope of doing yourself - they are a very advisable tool here. Try one before taking furthar measures if you have one to hand.

One option is to use an el-cheapo alan key (the kind you get free with self-assembly furniture) - or your worst screwdriver, and some superglue to attach a nice lever to undo the faulty screw.

I suggest you throw these away. This technique may also be used on "tamper-proof" screws when salvaging.

Failing this, you may have to go to the more extreme tactic of actually drilling out the screw. Get yourself a metal drill bit - they tend to be slightly harder wearing, and have a different blade angle from a general purpose bit. Then drill out the center of the screw - try to make sure your drill bit is around the same size as the original hole (if you know the diameter), as you may still want to be able to replace the screw with a good one later.

Building Tips
Retreiving Dropped Screws

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