Margin Marker - Gerikt'n Adjustable Marking Gauge, time-Saving Tool for Accurate Marking Along Straight Edges, Internal Corners, architraves, ply Sheets and cabinetry

I really love the Gerikt’n marker - primarily for reveals on casings, but handy for other marking tasks! Probably the best dollar-to-usefulness item I own. https://www.amazon.com/Margin-Marker-Adjustable-Marking-Geriktn/dp/B0B8SRH2G2