A form of screwdriver
with a square head. The primary advantage of the Robertson screwdriver is that the square head fits snugly inside the screw, and resists the screw falling off.
The screwdriver was invented by Canadian
Inventor Peter Lymburner Robertson
around the turn of the century, as a replacement for the flathead screwdriver
. He patented the system in 1908, which was soon used in the construction of the Ford Model T
car line. Robertson screwdrivers are color coded: green, red and black -- for different sizes of screws.
, over 85% of screws sold have the Robertson head. In the United States
, Robertson screws comprise about 10% of screw sales.