The intensity peaks within a solenoid beam are found in a spiral around the line of the beam itself, while a Bessel beam's intensity rises and falls in peaks and troughs at higher distances from the beam's line.
This exploits one of the predictions of Einstein's general theory of relativity: that the path of a beam of light (which is a straight line in empty space) is bent inwards by the gravity of a massive object.
More modern versions of the tool add in a laser beam projector, which allows builders to level out the device and "draw" a long line of light across a wall, indicating an exactly level surface.