Fig. 147 represents a plan and a vertical section of a line passing through the centre of the rail as before. From b draw bk parallel to cd; extend the lines id and jc until they meet k b in k and f; from n draw nl parallel to ob; through l draw It parallel to jk; from k draw kt at right angles to jk; on the line ob make ot equal to kt. Make ec (Fig. 148) equal to ek at Fig. 147; from c draw ct at right angles to ec, and equal to ct at Fig. 147; from t draw tp parallel to ce, and make tl equal to tl at Fig. 147; complete the parallelogram eels, and find the points o, o, o, as before; then describe the circles and complete the mould as in Fig. 145. The difference between this and Case 1 is that the line c t, instead of being raised and thrown out, is lowered and drawn in. A method of planning a cylinder so as to avoid the necessity of canting the plank, either up or down, will now be shown.