A bobbin on which to wind your plub bob string, that you can also click your plumb bob into. Makes it just that bit easier to store, or partially unwind. Designed for a 12mm diameter plumb bob and approximately 3m of string. If you need a different size, let me know and I can adapt the model for you. Requires a little bit of support at the bottom, nothing else. If you make one, please share the results!