This section is from the book "The Building Trades Pocketbook", by International Correspondence Schools. Also available from Amazon: Building Trades Pocketbook: a Handy Manual of reference on Building Construction.
In Fig. 24 is shown a method for determining the cross-section of a raking mold to miter with a given eave mold.
This method will apply equally well to any molding. The eave mold in this case is a cyma recta, the profile being shown as abfhjc. Divide the outline into any number of equal parts, as at f, h, j, etc. Draw any horizontal line Ik and erect perpendiculars from f, h,j, etc., cutting the line Ik. Draw al" at the required angle and draw be, fg, etc., parallel to al". From any point l', lay off the distance l'k' and subdivisions equal to Ik. Drop perpendiculars to al" from I', k', etc. intersecting be, fg, etc. Through the intersections thus found, trace the curve l' c', which is the profile of the required mold.
To find the profile of a vertical cut in the raking mold, at any point, as l", lay off I" k" and subdivisions parallel to Ik. Proceed to find points e, g, i, c", etc., as before.