Folding rule composed of three rods: two of wood, nine inches long, and one of brass, six inches long. The third is flat and slides into one of the first two. One side has three scales: the first numbered by 1 to 18; it continues to 24 on the brass leg. The other two scales are marked MH (Masthead) e YA (Yardarm) and were used for setting out the taper of ship's masts and yardarms. The opposite side has scales used for measuring areas and volumes.

This kind of instruments was used by carpenters in the building sites and shipyards. Provenance: Medici collections.