hand drill bits are drill bits where the thread of the drill is
reversed from a normal drill bit and they cut when the drill is
Left hand drill bits can be used to help extract screws which have
become stuck and the head is so damaged that it is of no use. Due
to the fact that the left hand drill bit is essentially trying to
loosen the screw as the bit moves into the screw it removes it providing
the bit "grabs" the damaged fixing successfully.