The Rifle Scope Ruler makes it easy to sight in a rifle with as little as one shot. Just place the ruler on the target after your first shot and get a direct readout of how many clicks to move the scope for windage (left or right) and do the same for elevation (up or down). It is designed for 1/4, 1/8, and 1/2 MOA turret scopes, and calibrated with scales for 25, 50, 100, and 200 yards. This MOA version is what most scopes sold in the USA will need to get sighted in accurately. The Rifle Scope Ruler will satisfy the demands of most shooters of modern rifles, muzzleloaders, scoped pistols, scoped crossbows, and scoped air rifles, from .177 pellets to the .50 BMG and beyond.