cordless screwdriver
Battery-driven screwdriver with interchangeable bits, used for tightening and loosening screws and bolts.
tip 
End of the blade or bit that fits into the groove of the screw or bolt.
reversing switch 
Switch for selecting the bit’s direction of rotation (screwing or unscrewing).
bit 
Detachable shank rotated by the motor to screw or unscrew a part.
battery 
Device that stores chemical energy while charging, then converts it to electric energy.
handle 