The nut on a stringed instrument like the nyckelharpa is the piece of wood (or sometimes plastic) over which the strings go on the neck of the instrument. Since it forms part of the system that sets the instrument tuning, and holds one end of the vibrating length of the string firmly to the instrument, it must be stable and solid. I used some dark, dense wood from my recycled piano collection – probably rosewood. It’s the same stuff the tuning pegs are made from.
You can see that I have arranged to screw the nut to the neck; this is so that I can exchange it for a better one, should I decide that I could improve on this first version. The playing strings are taken over the top of the nut (in the grooves); the sympathetic strings are taken through holes, as in the old kontrabas instruments.