Home improvement work is risky business. Children's cartoons serve as continual public service announcements of the hazards of "do-it-yourself"—stepping on garden rakes and putting hammers through thumbs tend to top the charts in terms of accidents. For traveling salesman Peter L. Robertson (1879-1951), however, a real accident in 1906, when he put a sharp screwdriver through his hand, prompted him to find a way of avoiding such accidents. By 1908 Robertson was manufacturing a screw that was to revolutionize the industry.
In Henry Petroski's book on the evolution of useful things he talks about the square-headed screw being invented to improve on existing designs—specifically the elimination or reduction of the risk of a slip. However, another improvement that Robertson made on the traditional screw was that his version could be fastened tighter than its rivals and operated with one hand—a very useful advantage for mechanics and other craftsmen alike.
The square-headed screw was simply a screw with a square cavity in its head and a pointed indentation at the deepest point of the hole. This guided the screwdriver into the cavity, juxtaposing it with the screw. This tight fit also provided sufficient torque to safely secure the screw into place more quickly than had previously been possible. It did not take long before the commercial benefits of this were recognized and, as a result, there were over 700 Robertson screws in each Model T Ford motor car that came off the production line. What had been a lack of sleight on Robertson's part in 1906 turned out to be a twist of fate that would earn this Canadian entrepreneur his fame.
