A method and apparatus for locating the intersection of the center of the web of a beam with a flat upper surface of an end cap of the beam. The apparatus has an upper portion that contacts the flat upper surface of the end cap and has ends that extend beyond the edges of the end cap. Arms that depend downwardly from the ends of the upper portion extend symmetrically toward one another. The upper portion has a predetermined point that is colocated with the axis of symmetry of the arms and an upper surface of the upper portion. The ends of the arms are separated by a distance that is greater than the thickness of the web. When placed over the end cap of a beam, the apparatus is turned about the axis of symmetry until the two arms contact opposing sides of the web, thereby locating the desired web center. The upper portion of the apparatus is preferably made from a transparent material.