THE 2-MINUTE RULE FOR TYPES OF SCREW HEADS FOR SCREWDRIVERS

Carriage bolts are employed where by the appearance with the concluded portion is important, such as on carriage exteriors: the bolt is inserted from the surface in the section, with only the smooth head visible; the square part of the shank aligns with a square hole from the part, which offers counter-rotation as the nut is tightened without needi