Robertson screwdriver

A Robertson screwdriver is a type of screwdriver with a square-shaped tip with a slight taper (in the same way that flatheads, Phillips, Allen, and Torx have flat, ×-shaped, hexagonal, and hexagrammal tips, respectively).

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.

The drivers are famous for holding onto screws (you can start driving a screw horizontally into the wall, and leave the screwdriver in the screw while you have lunch), and allow for things like an angled screw driver and trim head screws.

Robertson screwdrivers have a color coded handle for easy selection. The colors are Yellow(?), Green(#6), Red(#8) and Black(#12).

The Robertson screws were used in the construction of the Ford Model T car line, but today are scarce in the US, while being very common in Canada.