The Universal Saw Indicator is a 2 in 1 tool: Miter slot to table saw blade alignment calibration and table saw fence micro adjustment indicator!
It is used to measure the alignment of the table saw blade relative to the table (and the miter slot) to allow fine adjustment of blade parallelism. When adjusting fence spacing relative to the blade, it can also be used to measure very small changes in fence parallelism. Attach it to steel cross fences (which ride in the miter slot) or to ferrous table saw tables. The indicator is attached via an adjustable slot, allowing it to slide to fit a wide variety of miter slot spacing.