Rocks are wonderful to build with, but seldom come in the exact shape and size you want. For hundreds of years quarrymen have used feathers and irons to quarry rock to size. Now, on a smaller scale, you can do the same thing.
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. Voilà! 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.