Make wooden moulds, wrought inside, of the dimensions and shapes of the heads and sills, arranging one side to be removable, as shown in the sketch. Wedges driven through iron straps tighten up the mould when it is to be used. For the concrete, take one part by measure of Portland cement, one part of clean sharp sand, and three or four parts of broken stone, gravel, or broken brick of, say, 1-in. gauge. Turn these over on a boarded platform while they are dry, then, while water is being sprinkled on from a watering-can, turn the whole over twice or thrice, taking care not to use more water than is necessary to bring the cement and sand to the consistency of good mortar. The mould in the meantime should be coated inside with linseed oil or soft soap to prevent the concrete sticking. It is laid on a boarded floor, and the concrete is filled in and punned with a rammer to well fill the corners of the mould and to ensure solidity. Leave the concrete about 1 in. below the top of the mould, and float up this portion with a mixture of equal parts cement and sand, so as to form a skin of finer stuff for the surface that will be exposed to view. The mould must now be left undisturbed for two or three days, when the wedges may be knocked out and the window-head removed.

Before being used, the latter should be stacked away for ten or twelve weeks - the longer the better- to bring out the strength of the cement. Sills can be made in the same way, but the moulds are a little more elaborate.

Forming Concrete Window Sills and Heads.