Large field stones may be too much to move or too large to use. In either case, you will want to carve up the large stones into manageable pieces. Several tools can be used for gross cuts, beginning with an 8-pound sledgehammer. Stone cutting requires a metal straightedge. Use the straightedge to scratch the gross cuts into the stone with a pencil, chalk or a nail. Striking with the edge of the sledgehammer face instead of the flat surface turns the sledgehammer into a more precision instrument. Striking with the edge along the lines you've made begins to make micro-fractures. After ten or so passes with the sledgehammer, you can switch to a 16-inch mason's pein hammer. Using the beveled edge, deliver firm strikes to the line you struck with the sledgehammer. The stone will usually fall apart along the line.
Rough shaping -- or pitching -- of the individual pieces involves taking off large protrusions and establishing a rough outline for the eventual shape of the field stone. For this, you'll need a 3-pound or 4-pound drill hammer, also called a strike hammer. The strike hammer is basically a one-handed sledge for striking chisels. The chisels you need for pitching are solid metal chisels from one to four inches long. Pitching chisels have relatively blunt edges without carbide tips. Be careful with pitching chisels, because they break stone with some authority; you don't want to shatter or split the main body of your field stone.
Tracing and Shaping
Tracing is cutting the outline of the field stone with more precision in order to fit the stone. For tracing and shaping, you will need your strike hammer and tracing chisels -- from ½ inch to 2 inches. Tracing chisels sometimes use a carbide tip to maintain the edge; the tracing chisel edge is sharper than the pitching chisel edge. Tracing chisels are used to "nibble" the stone away along your preferred lines. Along with the tracing chisel, a brick hammer is useful. Trace chiseling will leave rough spots along the edges of the stone, and a brick hammer is useful to tap away those rough spots without splitting the stone.
Pointing and Flaking
Sometimes, your field stone will have a bump along a flat surface that isn't accessible to the flat chisel. This is when you need a point chisel, which is sometimes called a hand-point. The hand-point has a conical tip instead of a bladed edge, and it is used lightly with the strike hammer to take out raised areas a flake at a time, to prevent shattering or splitting the stone. Some masons like to flake the edges or surface of the stone for a decorative effect. For this, use the ½-inch tracing chisel with light taps by the strike hammer.