Fig. 117 shows an open sand mould in course of preparation. This is very simple and demands no particular skill. Two boards, A and B, are imbedded on edge in the foundry floor and are leveled along their length and across from one to the other. The sand between them is tamped down and leveled off by a straight-edged board drawn along A and B, and a tracing of the plate to be cast is marked on this bed of leveled sand. The outer edge and the center core of the mould are formed by pressing damp moulding sand with the hand firmly against wooden segments made to the necessary curvature. The center core will core a hole in the center of the plate, and smaller holes may be cored anywhere desired in the plate by small baked cores C, C, which are kept from floating or washing out of position by convenient weights, as at D. Lifting-lugs are provided at the edges of the plate. This is a type of plate frequently used to form the top of a loam mould. Small projections or prickers are usually cast on the under side of the plate to assist in holding the loam coating which the plate must carry as a part of a loam mould surface. Impressions are made for these prickers by sticking holes in the sand with a small stick, or the prickers may be formed by sticking two-inch nails in the bottom of the mould so that metal poured in the mould will solidify about the nail heads.

Fig. 118. - Example of a Small Green Sand Mould.