What are these pins for that I keep finding in my steel cabinets?
They are the remnants from the rivets used to hold the pieces of steel together. Each rivet contains a piece that holds the metal together and a piece that looks similar to a finish nail. When the "nail like" piece is pulled by the riveting tool it distorts the head then breaks off.



Pop Rivet set tool grips shank, draws ball head up through tube rivet to expand it till it bottoms out and breaks at neck inside tube rivet.