until the concrete is level with the top of the pouring form a bolt or a bolt securing device is placed in the center of the piling the distance between the pilings is equal to the length of the sides of the prestressed slabs a base plate 38 shown in fig2 and 4 is attached to the top of the pilings by a bolt or other suitable means of attachment the base plate comprises a flat plate with four protrusions 40 extending perpendicular to the surface of the plate when the base plate is attached to the pilings the protrusions extend in an upward direction from the base plate the protrusions are spaced so that when four slabs are aligned adjacent and corner to corner to each other the protrusions align with each of the four holes 36 in the underside of the adjacent corner posts of the slabs the slabs are attached to the base plate by slipping each of the holes in the lower end of the corner posts over each of the protrusions on four different but adjacent base plates attached to four adjacent pilings slabs are laid adjacent to each other in this fashion until the desired area is covered a second use for the prestressed concrete slabs is as a fencing material a concrete footing is prepared in the footing are placed two sets of flat anchoring plates one set on each side of the footing holes are placed in the anchoring plates so.