Matching Curves With A Tick Stick
by David "Shorty" Routh
https://www.shortypen.com/

Matching an outside curve is fairly easy by using a spline (which I like to call an offset tool) such as I describe on a web page about making a bunk for my Holder 12

Matching a inside curve is almost as easy, you just have to do it in reverse. This method is called using a tick stick, which is basically any pointy stick with a couple of marks on it. All you do is suspend a recording board or piece of cardboard in the area you would like to copy. Then you move the tick stick along the curve, and mark the various points on your recording board.

After you have enough points marked on the recording board, you remove it and place it onto the piece of cardboard. Move the stick around and match it back with all of the previous ticks, and at the point of the stick mark a dot. Connect the dots, cut it out and see how it fits.