To gauge and undercut a board a marking gauge (a tool used to mark a straight line across a piece of lumber) was first used to make a line exactly one inch below the top of the board. Then the carpenter would use a wooden rabbet plane to remove a narrow strip of wood on either side of the board down to the level of line. Next, the location of the floor joists that the floorboard would be laid over would be marked onto the back of the floorboard. Then, using a traditional adz, the carpenter would remove only the part of the board that was located over the joists down to the one inch marks, allowing each board to be exactly one inch thick when set on the joists. Through this process it was possible to quickly produce a floorboard that would lay flush with the neighboring floorboards.