Simple bar gauges are among the most useful tools in a shop. Much like cabinet scrapers, once you have used them, you wonder how you got along without them.
They have two primary purposes, comparing measurements (such as ensuring equal diagonals in drawers or carcasses to guarantee squareness) and transferring measurements.
Any time you can transfer a dimension directly, without converting it into numbers, you avoid a primary source of error.
Bar gauges not only shine in basic measurement transfer, but are unequalled for inside measurements, such as for sizing shelves or interior trim in windows. They can also be used as "story sticks" for complex built-ins where nothing is square.
Gauge head openings are 12.7 x 19.0mm; you just rip 6.4mm slices off standard 19.0mm lumber to make bars of the length you want (wood is not included). Made of brass and ABS plastic.
Now included are two brass pins for transferring inside or outside measurements smaller than the length of the sticks or for transferring outside measurements without making hook tips.