the amazing laser marker a new technology can project a 50ft. red laser line on the wall which help you to measure a balance level for hanging up a photo, fix an equipment....without problem & make sure the line is straight & parallel. the latest reflective lens technology, project a perfectly straight line on any surface. a great diy product for helping to hang up a photo, fix equipment. built-in levelling bubbles (2) to make sure the laser line is straight with 2 adhesive gum feet, will not leave a mark on the suface operated by 2*aaa size batteries ul listep 1) open the battery compartment & you will see two pins take them out if the wall is wooden./li listep 2) put 2xaaa size battery into the battery compartment then close the battery door./li listep 3) for wooden wall, put the pins at the front & rear of the unit in order to increase the stability of the laser marker on the wall./li listep 4) stick laser marker on the wall (resusable sticky pads included)where you want to show the laser line/li listep 5) press the button to project a 50ft.red laser line on the wall then you can put the object on the wall straight first time every time. /li /ul