I have designed these because I want to make a delta style 3d printer and use the beams as rails.
I have not tested these as I have not built my 3d printer yet but it should work. I used drawings made by openbuilds to determine the size of slots and the depth of slots. These are designed to be used with openbuilds M5 nuts and bolts.
I have left the plates as lineart so that you can plug it into a laser cutter and cut it out of 4mm thick steel.
File format: DWG
To import into sketchup go to file then click on import. select the DWG file and click on the options button to the right. tick all three tick boxes and set units to mm. Click ok and import it. To check scale is right use tape measure and use measurements from the pictures here.