Measure the amount you would like to cut off the wall cabinets from the back of the cabinet and mark it with a pencil.
Draw a line around the entire cabinet using a straight-edge and a pencil.
Cut the back of the cabinet off using a circular saw. Cut slowly to avoid jagged and rough cuts.
Remove the sides from the back that was previously cut.
Place the back onto the cabinet. Attach it to the cabinet with 1 1/4-inch grabber screws and a power drill.