Measure the gap in the wall to determine the length of ledgestone you need to cut. Allow room for mortar all around the cut piece.
Mark the line to cut on the top face of the stone.
Put on safety glasses and a dust mask for protection from any stone debris.
Cut along the line you marked on the top face of the stone using a table saw or circular saw.
Trim off any irregular protrusions using a hatchet. Shape the stone as desired using wide-mouth nippers to add texture.