Open the battery compartment by pressing down on the rear of the device and pulling up on the front.
2. Insert three new A-76 batteries into the battery compartment with the positive side of each battery going in first. Slide the open side of the switch/battery compartment into the front end of the bore sighter. Press the rear of the compartment into the bore sighter.
3. Close the battery compartment by pushing down on the front and lifting up on the rear.