Second, build a wooden form in which you can pour a concrete ring sill that is four inches thick with outside dimensions of 4'10" X 4'10" and that has a hole in its center measuring 3'8" X 3'8". Pour the ring sill and center and level it over the excavation.

Next, build another form in which a slab of concrete four feet square and 2 1/2 to 3" thick may be poured. If this slab is poured flat (as shown on this double-page spread), a wooden riser box with cover will have to be constructed and mounted on the slab later. The riser may also be made of concrete and poured as part of the stab as shown on page:

All concrete, of course, should be suitably reinforced with steel rod with eye and anchor bolts imbedded in the sill and slab as needed.