For an oblique tee-pipe (Fig. 11), in which both pipes are the same diameter, the elevation of the two pipes is set out to the required angle, and the pattern marked out in the usual manner. The shape of the hole can be obtained as in Fig. 8, or scribed directly from the pattern, the curve at top of hole being the same as the curve from b to c on pattern, and the
Fig. 12, heights a b being equal. The two halves of pattern are exactly the same, and after what has been said with regard to Fig. 9, the mechanic with an ingenious turn of mind will probably be able to see how the two curves on half of pattern can be used to set out an obtuse elbow and an acute elbow at the same angles at which the centre lines of the two pipes meet.