With many fittings, there is usually one area that requires more attention to figure out the correct points needed to develop the pattern. That’s why you should keep your fittings symmetrical if possible.
It helps if you can visualize fittings as well.
Shown in Figure 1 are two views - the top and elevation view. The top view shows the top of the fitting (round) and the oblong base of the fitting, as they appear perpendicular to the plane. Because the two sides are straight, since this fitting only tapers on one side, the radius will be the same for the top and the base. From the top view, one can see the overall length and width of the fitting and the radius ends. The elevation view, Figure 1, shows the height of the fitting (true length) and shows the true length of the taper side.
In Figure 2, some of the area that you do not need to draw as you develop the pattern is shaded. All the information you really need is in the one-quarter of the drawing and is for helping you determine the true-length lines for the tapered side.
As for the shaded area, from Point A to Point A1, and to the left of this line, is the length of half of the circumference of the top round. If this fitting is being created in two pieces, then you’ll only use the length from Point 1 to Point 4b - and add this length to the end of the pattern.
Because the radius is the same for the top and the oblong base, you only need to establish the points on the one section, Point 1 to 4a, as shown. Divide the circle into equal sections, as shown from 1 to 4a and reference them. Note that this line or part of the radius you are dividing is in its true shape. Each division or section of the circle is in its true length and it must be true length in the pattern.
Develop the elevation view as shown in Figure 2, by projecting lines down as shown from points A to A1, B to B1 and 4c. Drawing a line perpendicular to the projected lines establishes the base of the elevation view. Measure up from the baseline to establish the height of the fitting and draw an extended perpendicular line from Point 1 to Point 4.
On the elevation view, Figure 2, draw a line from Point 4 to intersect the projected line drawn from Point 4c on the baseline of the fitting. This is a true-length line for 4a to 4c. Draw an angular line from Point 1 to B1, which is also a true length line. This establishes the side, the triangle of points 1, A1 and B1, shown in its true shape. You’ll be using this shape to develop the pattern.