Sure thing: I don’t have pics of the ones we have in the shop but here’s one from YouTube – they’re table saw sleds like this:
(it sounds like we have a couple of slightly different versions in the shop)
They’re not absolutely necessary because you can just cut ring segments on the miter or table saw anyway, but the jigs make it faster and more accurate, as usual. The original “wedgie sled” design is from here but this is a shorter explanation of how they work:
The clamping jig I referred to in my previous reply is like this:
