This excellent information; thanks for the write-up and links! The Always Rights are definitely an imperfect solution for trying to attain a “perfect” right angle (like you said, nothing is perfect…there are always tolerances). I really should have framed it more as a “quick set” solution for getting straight-cut pieces relatively straight on the bed. I know I like to play chicken with the edge of material on cuts so as to save as much as possible, and it’s always harder when you realize you put something down a bit crooked. The Always Rights can help with that, but they definitely don’t guarantee anything is perfect. There are so many variables to account for!
I hadn’t come across the tray boots before, but those are great! I’ll definitely be making a pair. I recently made a non-consumable jig for cutting/engraving four coasters at once. It’s a piece of 1/8-inch-thick dry erase board (from Lowe’s) with four 4-inch squares cut, and a guiding cross-hairs scored in the middle (I pre-cut 4-inch squares of material on my table saw and place them in the jig, then make my coasters no large than 3.8 inches in any direction). The dry erase material is nice because smoke/soot wipe off with a cleansing wipe.
I cut the jig to be the same width as proofgrade material because that at least sits consistently snug with the sides. Pins at the top and bottom help keep it from shifting vertically, but I hadn’t considered the risk of the bed itself shifting. The boots will definitely help prevent that. Making that jig was also what taught me that the GF isn’t square itself, because I quickly realized that my crosshairs didn’t work as well if I put the jig in upside down (relative to the way it was cut).
Also, thanks for reminding me of the word “orthogonal”. Trigonometry is definitely the most useful math I took away from formal education, but I’d somehow forgotten that word.