I used this setup to make low-poly versions of all my pots and pans so that I could model them in SolidWorks and create custom storage in my kitchen drawers. The basic setup is three rulers connected by two sets of knobs. I find the initial radius of the top and bottom of the pan, overlay this ruler setup to a snug fit, then count the ridges beyond the top and bottom edge to find out how much length I need to add to either radius to create a cavity that will store the pan securely. Each ridge in the ruler is 1mm, and each space is also 1mm. When first assembling, start with the male threaded knob, nestle one ruler onto the square extrusion, then stack the second ruler, then the washer, then the female knob.