Cross & crossline Laser Tools are fantastic for those times you you need a long straight line ether horizontally or vertically. Cross & Crossline Laser Tools are great for using to make sure objects are perpendicular to one another. This works great for projects like tile work and wall moldings and paper. Often self-leveling, this gives you the advantage of a simple "stick-and-go" measurement, without the tedious problems of having to level the laser yourself. Simply turn the unit on, place it on the wall or floor, and get perfect lines!