While playing with my Moon Rover tread, I found it zipped into itself pretty well. This is an adjusted version that can zip into both sides. It's flexible in several dimensions and easily layered. It's quite fun, and I'm curious what uses or interesting shapes you all can come up with for it.

I can't get Skeinforge to skein zipper.stl, so I'd recommend printing zipperSolid.stl with fill turned off, so it just prints the perimeter. That'll make two zippers, which you can cut apart with scissors. Cut the loops off so they look like zipper.stl; that'll allow them to hook into each other end to end as well as side to side.

The OpenSCAD file is fully parametric; only four parameters define the shape and they're all up front in the code. It's set for a thread thickness of 0.42mm, which the TOM MK6 default for 0.3mm layer hieght. Just read the thickness out of RepG and put that value into the scad file.