The gantry section is complete, and so far: no fancy machine shop tools were needed in the assembly.
To Tension the belts, the center plate joins the belt ends together with a delrin sandwich: two plates, one flat, one grated. The grating does the heavy lifting of holding the belt in place while the screws prevent it from slipping. I've seen a few different ways to tie down belt-ends, some often cleverly wrapping the belt back on itself. In this case, though, I've tried to keep it simple and fairly easy to duplicate.