My husband has a drawer full of fasteners and other hardware that he keeps just for spare parts and for those situations when something needs to be fixed.  However, it’s usually the rule that whenever you need a certain part – for example dowel pins for a broken shelf – that part is nowhere to be found in the spare parts drawer.  More often than not, my husband has to run to the hardware store to grab a brand new package of screws or whatever else he’s missing.