The treenails are 25 to 28 mm round and tapered at the inboard end, and are fabricated from split oak made round with a rotating plane. The head is finished and bevelled with a rotating tool that leaves a mark in the centre. On the Mary Rose, the contrasts are numerous. At each joint of a plank and a frame, two treenails are found, measuring 25 to 30 mm round and centred on the frames. A countersink does not appear and the outboard ends are feathered and spread by the insertion of hemp caulking.
Many studies indicate that fasteners vary regionally.
J. B. Lavanha stated that metal nails were preferred for warm seas rather than the treenails used in northern waters which were vulnerable to teredo damage. A. E. Christensen recounts how treenails were fabricated in homes by children during the winter months to augment family income, while Biscayan metallurgy in the 16th century was a large-scale, intensive activity that produced vast amounts of iron nails for shipbuilding. All attempts to relate the assembled frames to the madeiras da conta in shipbuilding treatises have relied on indirect reasoning. No such assembled frames have been found on the Mary Rose. Both master frames were designed using identical principles.