Clout type round plain shank nail.
Also known by names such as copper roofing, slating and flashing nails.
They have a wide flat head and smooth shank and are a good alternative to galvanised nails.
Besides sheathing of boats, they are used for slate roofing where their ease of removal, corrosion resistance and malleability is valued. They are also used for straps, gutters, furniture and wooden planked boats.
Traditionally used to hold copper sheathing (thin copper sheet) to the hulls of timber ships. The copper reduced attack by wood worm and growth of barnacles oysters etc., thus increasing the boat speed and improving hull life. The copper sheath required regular replacement and as such the nails are plain shanked to aid in their removal.