Kossel Slide Carriage Alignment tool

I noticed there is lack of tools for aligning Delta printers. We are instead relying on the quality of the print and a prayer for getting the geometry correct. I would like to standardize on a set of tools for validating the physical geometry of deltas is correct. This is the first tool.

This is a concept tool for aligning the Slide Rail carriages on a Kossel Mini. The carriages need to be perfectly parallel to the towers (or slide rails). The mounting holes allow of a small bit of play whi