Scribing is the act of marking material that has to be removed from a counter or piece of trim so it fits tight to a wall or cabinet. Carpenters typically perform this operation with scribes, an adjustable marking tool similar to the compass used by a geometry students. Most carpentry scribes have a sharp point on one end and a pencil, lead, or second sharp point on the other.
The goal of scribing is to create a cut line perfectly parallel to the surface the trim is being fit to. With conventional scribes this is done by moving the scribes along the wall with the point against the wall and the pencil on the component that is to be cut.
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The Thingamejig does the same thing as scribes but in a slightly different manner. It has a three-winged head with replaceable carbide cutters screwed onto each. The distance between the foot—which rides against the wall or surface being scribed to—and the cutters is adjusted by turning a threaded shaft. After dialing in the desired setting the craftsperson secures the shaft with a lock nut.
Scribing baseboard to the floor means creating a cut line that is perfectly parallel to the floor.
This device allows you to create an extremely fine cut line and/or score the surface to reduce splintering when you cut. Unlike a pencil point (which is soft and subject to wear) or the scribing point on a set of scribes, the carbide cutters are sharp enough to leave a fine line and cut slightly into (score) the surface of the piece that's to be cut. The ability to score comes in handy when scribing across the grain in veneer plywood.
A removable plastic cap can be snapped over the foot to prevent it from marring delicate surfaces.
The triangular blades can be rotated to expose a fresh tip and replaced when all are dull. Being carbide, they should last a very long time.
Scribing a laminate counter top to the wall.
The Thingamejig works best when used to scribe to straight, smooth, or flowing surfaces such as fitting countertops cabinet fillers and trim to ceilings walls and floors. It's not an all-purpose scriber and won't scribe around moldings and irregular surfaces such as stone. Fortunately, there are plenty of other scribing tools that can do those things.