The Bosch GLL 3-15 self-leveling three-line laser can help with alignment, leveling and squaring needs. Bright laser lines can be used in self-leveling mode or locked in manual mode for sloped applications. The unit features an audio alarm to alert that the tool is out of range in self-leveling mode so you can build with confidence. The GLL 3-15 is versatile to use thanks to the BM3 positioning device. This included device allows the user to position the tool on any flat surface, attach it to metal surfaces or clamp it in place for ceiling grid applications.