Ratcheting screwdrivers are In particular useful in tight areas in which you don’t have plenty of clearance to carry the screwdriver to reposition it. Slot measurement: There are only 3 or 4 typical measurements for Phillips and Robertson screwdrivers, but there are many far more for flat-head, Torx and hex-head. https://andyzkepa.theisblog.com/29580464/the-greatest-guide-to-what-is-a-lead-screw