The Sonic Screwdriver is a versatile tool and defensive device first used by the Doctor in his second incarnation for opening up hatches, panels
Later uses included cutting through wall sections and even as a conventional screwdriver. During the Fourth Doctor's reign, he remade yet another
similar style of Sonic Screwdriver but with many more features and functions including micro soldering of circuitry, cutting wires and bulkheads
and even detonating Dalek explosives.
An electronic version of the Fourth Doctor's Sonic Screwdriver with sound fx bzzzzzz.