Umbrella Stampis an optional part and a bit fiddly.It maked sure that the M4 bolt doesn't deform your umbrella as cheap umbrella-holders without such a stamp do.When not in use, screw the M4 bolt all the way in. This way the Umbrella Stamp doesn't fall out.The M5 nut(s) goes into the inside of the base part and are held in place by their respective M5 nuts.1 should be enough but you can use 2.