Long before the power drill became a fixture on every construction site, driving a screw by hand was slow and hazardous work. Into this trade stepped Peter Lymburner Robertson, a travelling tool salesman from the town of Milton, Ontario, and from an early age he was fascinated by the mechanics of everyday hardware. Certain accounts relate that the notion for his most famous invention came to him after a slotted screwdriver slipped during a sidewalk demonstration and gashed his hand. Determined to design a fastener that would not let a blade skid free, he shaped a screw with a small square hollow in its head and, around 1908, opened a factory to manufacture it. Some historians suggest that tinkerers had toyed with square recesses decades before he refined the idea.
The most distinctive feature of Robertson's fastener was undoubtedly the square socket sunk into its head. The recess was tapered so precisely that a matching driver wedged itself firmly in place; a worker could balance a screw on the tip of the tool and drive it home with a single hand, even while perched on a ladder. The screws were forged from hardened steel, and the sockets were colour-coded by size, so that green, red, and black tools corresponded to particular gauges. Because the blade seldom jumped from the socket, the surrounding wood or metal escaped the scratches that a slipping tool would otherwise leave.
