Page 7.8a.

The next step is to bring these WIDTHs up to the XY, there are three methods of doing this, this page, and the following two will show them, you choose which you find easiest.

Method 1 :- Using the compass.
Place the point of the compass where the XY and the YY meet and swing the points a, b and c on the YY up to the XY, as shown below. We then project them up for the End View.These are construction lines, so remember to keep them light.