Bright red or green beam laser dots measures level or plumb using precision level vial or two plumb vials that are built in and factory set, Turn the laser on by turning the battery cap, Mark the center of the laser dot and subtract 1/2" to reference the bottom of the level, Working edge is machined flat to 0.005", Solid aluminum frame - one piece case design won't bend or twist and it's weather protected, Recessed level vials are easy to read, but well protected, Features industrial grade optics that are fully coated for maximum performance and 1/4" - 20 thread mounting hole can be mounted to standard camera tripods for stand alone operation, Solid brass end caps provides for years of trouble free service, Optical calibration - no set screws and Wedge prisms factory calibrated - no field adjusents required, Ideal for site layouts, crosscut measurements, slope, conveyors, grade and transit work, Battery operated with over 30 hours of continuous operation, 40-6242 Includes > Laser, 2 AA "MN1500" alkaline batteries, instruction manual