[thstone]

Usually when the barrel of a hex head bolt starts to strip from being overtightened, only those sides/faces of the bolt for tightening are deformed - the opposite sides/faces of the bolt used for removal are hopefully undamaged and the bolt will come right out. If not, use the next size up hex head or a torx or a specialty removal tool (e-z out) that is left-handed and will bite into the barrel material for removal.