Caulking

Caulking is both the technique and the material (or sealant) used to make vessels watertight.

Traditional caulking on wooden boats uses cotton and oakum (hemp fiber soaked in pine tar). These fibres are driven into the wedge-shaped seam between planks with a caulking mallet and a broad chisel-like tool called a caulking iron.

The caulking is then covered over with putty if in seams of the Hull, or with melted pine Pitch if in the seams of the Deck.

It's important to remember not to overcaulk, as the cotton and wood will swell when wet.