Caulking

If the sawyers were the first to work on the new hull of a new ship, the caulkers, who filled the seams between the planks on the sides and decks of the ships, were the last. According to Burney’s Universal Dictionary of the Marine, to caulk was to drive a quantity of oakum, or old ropes twisted and pulled asunder, into the seams of planks in order to prevent the entrance of water. After the oakum is driven very hard into these seams, it is covered woth hot melted pitch or tar, to keep it from rotting.

Caulking Ships at the Bothuisje on the Y at Amsterdam by Reinier Nooms

That means that a caulker used a beetle ( a caulking mallet) to drive reeming- irons with the rope or the oakum into the seams.The seams were gone over with a hardening iron to firm up the caulking material in them before they were sealed with pitch or tar.

A caulking mallet, tar pot and a piece of petrified tar found on board the 16th century Mary Rose and Caulkers at work 

It was unpleasant work which offered none of of the satisfaction of an shipwright in seeing a huge and beautiful hull take shape.

Ships Careened for Caulking the Hull, 17th century

Caulkers often had to work in uncomforatable positions and in 1724 the Deptford officers reported that they cannot in the winter season see to perform their day work in the dock as it ought to be unless they work their dinner time, it being so dark under the ship’s bottoms between three and four o'clock in the afternoon…