This thing is a part of Contraptor - a DIY open source construction set for building Cartesian robots: http://contraptor.orgSliding elements slide on perforated angle http://www.thingiverse.com/thing:1066, driven by either leadscrew or belt. There are three sizes of the sliding element: 3.5\", 2.5\" and 1\". The part list is for 3.5\" size.Sketchup source: http://sketchup.google.com/3dwarehouse/search?q=contraptor+sliding-elementSliding element is basically aluminum square tube with UHMWPE pads. The square tube pieces are made using SVG templates. UHMWPE pads are cut out from channel stock, drilled and fitted inside, held by plastic screws. Some hacksaw (or Dremel) work is required to thin the areas where UHMWPE pads touch the angle rail. The friction is adjusted by small screws.Detailed howto: http://contraptor.org/make-sliding-elements