The Naildriver has a 10-click knob for computer generated sight tape compatibility; it's proven to be the toughest, most reliable target sight available on the market to date. This particular model is completely hand machined and match milled to perfection with Toxonics patented locking mechanism. Depress the lock knob for rapid movements; a single twist of the knob locks sight block and lead screw for twice the locking power and repeatability of other sights on the market.