Screwdriver Bit Square (SQ)
A Robertson, also known as a square or Scrulox screw drive is specified as ANSI Type III Square Centre and has a square-shaped socket in the screw head and a square protrusion on the tool. Both the tool and the socket have a slight taper.
As patents expired and awareness of their advantages spread, Robertson fasteners have become popular in woodworking and in general construction. Robertson screw bits are easy to use one-handed, because the tapered socket tends to retain the screw, even if it is shaken.
Universal hexagonal shaft in 6,35 mm (¼ inch)