Using a 3/4" masonry bit (available at most hardware stores), you drill holes along the intended line, hang a pair of feathers (shims) in each hole and insert the irons (wedges). Then tap the irons deeper and deeper until the pressure splits the rock. Voilą! With a bit of practice, you quickly come to know what hole spacing to use on different types of stone.
Comes as a set of three irons and six feathers.