The GSL2 surface laser projects a pair of beams onto the floor; the beams intersect to form a single line at the elevation of the benchmark – the reference point from which the rest of the floor is measured.
A knob on the base can be used to raise or lower the tool so the beams converge at the desired elevation.
The beams project from the laser at an angle and meet somewhere at, above, or in theory – below the level of the floor. I stood up this piece of plywood so you can see the angle at which the beams come out of the laser.
These beams meet to form a single line on the floor, so this section of floor is at the elevation of the benchmark.
These beams cross before they hit the floor, which means this part of the floor is below the benchmark.
A target is used to measure how high or low a particular point on the floor is in relation to the benchmark. This point is 3/8” higher than the benchmark.