The fourth form in the layout system, and the first that leaves the page. The others set where an edge goes; these set how far it stands up.
Every other form in this system answers the same question: where does the edge of the panel go. These answer the one that leaves the page — how far does each piece stand up. A jig is a shallow polygonal funnel with flat facets falling to a common centre, so the pieces you lay in it all rise at exactly the same angle and meet cleanly along every seam.
The number on the jig is the angle the glass actually sits at. Not the cone angle, not the fold between pieces — the dip of the facet, which is what a protractor laid along a petal reads. On six facets those differ by fifteen percent, so it is worth being exact about which one you are buying.
The whole set bolts into one stack. A post runs through the middle, a keyed head screws in underneath and a knob clamps it down on top. There is no case because there is nothing to put in one: assembled is how it lives on the shelf and how it comes out of the box. The post is cut to the same number of sides as your jigs, so every piece of glass butts squarely against one flat face.
Metric or imperial, in three sizes each. Three, four, five, six, seven or eight facets. Six is a six-petal flower; two adjacent facets of a four is a butterfly's wings; eight is a rosette. Take all seven angles, or the round numbers, or the halves — the two half-sets partition the full ladder exactly, so buying one of each completes the set with nothing duplicated.
Every jig carries its own angle embossed on two faces, proud rather than engraved, so it reads on a shelf and prints without a pocket to fill.