On a hand stapler you have a silver metal anvil on the base of the stapler. This anvil is where the staple legs are formed either in an inward (standard clinch) or outward (pinning) fashion.

Pinning (the staple legs are formed outward) is an old style of securing papers. You would be able to remove the staple without damaging your papers, and add additional papers. One draw-back to this style of fastening is that the staple leg is exposed and will catch on other objects.