Using half a shoe, begin by splitting the shoe between two to three nail holes, depending on the width between them and the size of shoe. Slit the hole undersized by approximately ½?-?¾ of the finished size, as the tab of metal left on the cut end will become part of the volume of metal in the ring, increasing its diameter. After slitting, clean up any ragged edges to prevent cold shuts that will weaken the opener’s ring. Cold shuts are areas where two pieces of metal aren’t fused together—in this case when a ragged edge folds over into the ring without welding to the parent metal, creating a thin point.
Begin to open up the split by hammering your slitting chisel deeper. Continue opening the ring with punches until it will fit onto the tip of your anvil horn or mandrel. If you don’t have an anvil with a horn, you will need to make a mandrel to round the bottle opener. A simple mandrel is a 2-3 inch rod pointed on one end and held in a large vise.