Caulking

The caulking is the millennia old tecnique that makes the difference between a wardrobe and a boat: both are made out of wooden parts, connected to serve a purpose and to resist some loads. But if they are thrown into the water, the wardrobe content is soaked, the boat's one is dry.
Even the Bible, when Noah got instructions to build his boat, mentions generically an "ark" (i.e. "a box"), but it dwells on the way to make it waterproof. And the same happens when it describes the basket which is entrusted with baby Moses' destiny.

It's a mostly forgotten art.
When a gentleman, looking for "Master caulkers", is addressed to the boatyard cave, Mast'Antonio replies firmly, giving him an address in upper Meta: the cemetery address..

But Mast'Antonio Cafiero is a modest man. Even if he's a boatwright "only", and not a caulker, he is perfectly able to execute the caulking on his own "gozzo", using the traditional tools inherited by his master.
They are a series of different chisels, apparently almost undistinguishable from each other, but to be used progressively, and a large peculiar mallet. The first chisels are used to enlarge the seams (the spaces between a plank and the other). Cotton weaves (or oakum on larger boats or ships) are then inserted into the seams, and forced in position with the next chisels, blunter than the others, effectively sealing them. On larger boats, like on the "gozzo"'s deck, seams are sealed melting pitch on the oakum or cotton, then sanding it to level it. But on a 7 meters long gozzo , parts are small and deformations due to strains are not significant compared to dimensions of seams, so plaster and paint are enough to complete the caulking.