Well, what do you know? It’s the centenary of the Robertson screwdriver. From Wikipedia:
A Robertson screwdriver (also called a square drive screwdriver) is a type of screwdriver with a square-shaped tip with a slight taper (in the same way that flatheads, Phillips, hex, and Torx have flat, ×-shaped, hexagonal, and hexagrammal tips, respectively). Robertson screws are used mainly in Canada, though they can be found elsewhere.
Canadian P.L. Robertson invented the Robertson screw and screwdriver in 1908. He received a patent in 1909, and later applied for and received other patents. The last patent expired in 1964.
Robertson screwdrivers are easy to use one-handed (i.e., without using the second hand to hold the screw), in fact, when driving a screw one handed, the user can let go of the driver, and the driver will stay put in the screw. They also allow for the use of angled screw drivers and trim head screws. [continue]
Thanks to David for writing to tell me about this.