About this 3D model

Bed levelling aid for 3d printers. Designed for the Colido DIY. Use V3 - slightly increase clearance to allow smooth sliding of ruler part. To use - go and buy a digital tyre depth gauge from ebay for about £3 (call it $5 in the US). Unscrew it, throw 2 pieces away, build this, clip onto appropriate axis and measure away. In my depth gauge there was a small metal spring which stopped the probe dropping under gravity - getting rid of this seems a good idea. The two printed parts are designed to be printed with no supports, you'll need to change the orientation that ive uploaded. I think this would also work for a makerbot since it seems to fit ! Comments and ideas for improvement please .....