The Trim Gauge by Brumley Tools
This could be the greatest manual measurement tool since the miter square. With a built in 3/16-in. reveal for setting trim around doors and windows, the trim gauge also has a depth gauge/scribe guide and levels for plum (sic) and horizontal. It’s great for scribing, setting depths on saws and routers, repetitive measurements, establishing reveals, trim and hardware setting and leveling, and other tasks where small gaps are measured and established.