Neoprene joist tape or u-shaped rubber spacers help decouple the subfloor from the joist. A "subfloor" of plywood or waferboard is then laid over the joists. When building subfloor the joists must always bear on the ledge for all it support. Subfloors above grade (above ground) typically have a plywood subfloor. They are also ideal for floor tile and stone installations over a structural subfloor. Sanding provides a method for smoothing an installed floor, compensating for unevenness of the subfloor. Its subfloor construction includes brickwork of an earlier building in this position. It also nests in ceilings, walls, and subfloor areas. A floor of offices occupied the level above this "subfloor" of stores. In modern buildings the subfloor often has electrical wiring, plumbing, and other services built in. The cobbles are pressed into the subfloor using a paving hammer. Each piece was dovetailed to interlock and to fit into a subfloor. A rear verandah has been enclosed and the rear subfloor space has been bricked in. Usually, the cobbles are set in a sand subfloor. The majority of the subfloor area remains undisturbed and a potential archaeological resource.