Abstract: A device comprising a body, having a cavity extending therethrough from a top surface to a bottom surface, may comprise a massive core enclosed by a cover. A recessed area on the top surface adjacent the cavity extends from the cavity to a perimeter of the body. A designated edge between the cavity and the recessed area is located a predetermined distance from an opposite perimeter. A releasable fastener or clamping device may be provided at the recessed area. A top and bottom post may be coupled together in a center hole in the body, to provide a center post from which to measure. Markings may be provided on the top surface of the body for measuring at an angle from the center. Small grooves may be provided in side surfaces of the body for aligning the device with lines or markings on the floor.