Assemble the battery 1. Put batteries into the battery holder according to the image display. 2. Insert the battery holder into boresighter's battery compartnent. 3. When the 2 points are aligned, boresighter is ON. When they're not aligned, boresight is OFF. 4. Rotate the battery holder to make the points be aligned. Select the proper adapter for your barrel 1. Choose right size adapter for your barrel. 2. Use the screwdriver to tight the screw into the adapter. Just make the size is fine to fix in your barrel. Insert the boresighter into barrel 1. Push the small end of the boresighter with the adapter into the barrel of your firearm. Make sure the boresighter is inserted in until it is sung with the crown of your firearm. 2. When you turn the laser on, a small green laser dot will be emitted. And then you can adjust your scope?s windage and elevation so that your crosshair aims at the green dot. HOW TO ADJUST IT? Adjust the laser up and down After loosening the above(below) screw with a wrench, slowly tighten the below(above) screw until the laser point is at the desired position. Adjust the laser left and right After loosening the left(right) screw with a wrench, slowly tighten the right(left) screw until the laser point is at the desired position. SPECIFICATION Material: Aluminum Weight: 1.34oz Length: 6.1" Big end Diameter: 0.63" Small end Diameter: 0.2" Laser Wavelength: 630-680nm Max. Output Power: <5mW Laser class: II Ia Laser Color: green Keep boresight laser pointing away from eyes