This thing is a part of Contraptor - a DIY open source construction set for building Cartesian robots: http://contraptor.orgA pair of shaft mounts with bearings support a threaded rod used as a pulley shaft or a lead screw.Sketchup source: http://sketchup.google.com/3dwarehouse/search?q=contraptor+shaft-mountThe shaft mount is made from aluminum angle stock. It has 3/8" hole for the threaded rod/shaft, surrounded by three 6-32 screws. The R188-2RS bearing fits in between the heads of the screws. Each shaft requires a pair of mounts.Detailed howto: http://www.contraptor.org/make-shaft-mount