A rivet is a short metal pin or bolt having a head on one end, inserted through aligned holes in two pieces of metal to be joined and then hammered on the narrow end so as to flatten it, forming a second head. Or, as with the kind shown here (commonly available in various sizes at hardware stores), a specialized tool is used to insert the rivet and pull out the pin, widening the end on the far side of the join. Riveting then is a method of joining pieces of metal (often sheets) using rivets.Also see steel sheet gauges.