I am fascinated by this tool, and intend to build one for myself.
In the log building of the Berner Oberland in Switzerland, cutting grooves the length of timbers is an important process. Grooves are cut to receive spines between timber courses, grooves are cut into the sides of uprights to receive tenons on the end of the horizontal courses, and so forth. Ancient methods involved the use of a narrow axe to cut grooves, other approaches involve scooped drawknives or gouges. Craftsmen over the centuries devised an ingenious tool for cutting these grooves. It's simply called a Nuthobel, meaning grooving-plane
The Nuthobel used for building is this:
Essentially, it is a standard grooving plane with a large adjustable fence, which rides up against the edge of the timber. It has a nut on the sole, with the back set slightly lower than the front. The blade is set in a position that cuts well, and the fence used to keep it always in the same groove. Quite an ingenious little tool
