Screw head is now too beat up to cooperate with a screwdriver? A screw exractor is one option.
http://www.acehardware.com/family/in...goryId=1259460
It's not a hex head screw, is it?
Are you removing a rack? Or, just adjusting it?
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Bacchetta Giro A20, RANS V-Rex, RANS Screamer