This cutter has a base for cutting over pad or other carpet that protects the material underneath. The blade carrier is adjustable in height so you can lock the beveled guide at just the right position to follow in the rows. The cutter has dual blade pockets on left and right sides, and a large thumb knob that tightens to lock in the blades. For best results, trim WITH (in the direction of) the nap sweep of the carpet. Beginning at a starting point on the left side of the seam, trim with a blade down on the left side of the cutter. Return to this same starting point on the right side of the carpet and trim with the blade down on the same (left) side of the cutter, moving down the seam in the same direction. This procedure simulates the factory spacing of the carpet's rows on most carpets. When necessary, to trim both edges as close as possible to the tufts, trim the right side of the seam with a blade down on the right side, then for the left side retract the right blade and trim with the left blade down.