Round Nuts Cylindrical nuts with machined periphery or seating surface (the side opposite to the mounting surface) for mounting. Normally two or four faces or holes are machined on the periphery and a hexagon socket or groove (+, -, cross, slot) is machined on the end face. All cylindrical shaped nuts are sometimes called round nuts. These also include round bosses (cylindrical nuts) for welding, knob (female threaded), insert crosses, and more.