XCSOURCE Right Angle 90 degree Vertical Horizontal Laser Line Projection Square Level Laser Square BI010 Laser Level Square is an easy to use leveling tool. Projects horizontal and vertical laser "chalk lines" on surfaces. Dual diodes for making 90 degree laser beams on any surfaces. Two suction cups allow the laser level square to be mounted onto the surfaces alignment guide for 90-degree layout-calculate and turning angles in 5-degree increments. Kindly noted: the angle of the laser line can be changed according to the angle scale, saving your time of measurement and marking.