An angle measuring apparatus includes a housing that has a circular aperture, and a rectangular slot positioned such that a length of the slot is in parallel with the circular aperture. A rotating assembly has a weight, positioned within the circular aperture and is operative to rotate, with the weight maintaining the position of the rotating assembly with respect to the housing as the housing is moved angularly with respect to a reference position, such that the weight position indicates the direction of gravity. A transparent insert, that has indicia for indicating measurement angles, is operative to be removably inserted into the rectangular slot such that the indicia are superimposed over the rotating assemble and operative for use as reference indicia as the rotating assembly rotates.