E.g. stripper clips, which are little strips of metal formed to hold the rim of five or so cartridges (a magazine load). You put the clip into a slot in the receiver above the magazine (in the case of a fixed magazine) or the magazine itself and push down on the top cartridge and all the rounds slip into the magazine. You then toss (or pocket) the clip.

Check this:
http://www.surplusrifle.com/pistolc96br ... ations.asp