Belt Tension Gauge
by ianjohnson, published
Checking the tension of the left and right Y belts to make sure they are equal can be a little subjective and uncertain. Use this to verify that they are the same, and have an objective reference for tension.
Load it up with quarters ($4.25) and hang it from the center of the upper belt. Count the number of notches (1mm thick, spaced 1mm apart) between the belts.