A collar that you can screw onto the standard neck bolt of a Dremel Multitool. It's designed so that you can print out 2mm-thick stencils and use this to trace them with a router bit, so you can precisely cut out small bits of timber etc (using a Dremel router bit). I haven't actually had great results using it, but the screw thread fits perfectly on my Dremel, so you may find that useful if you're designing something similar using Rhino. I've included the Rhino 3DM file with my working.The two parts are designed to print without support, and then be superglued together. It should be pretty self-explanatory...