Beric the Briton by G.A. Henty

That evening Beric had a long talk with Aska and four or five men from the coast accustomed to the building of large boats. The matter would be easy enough, they said, as the boats would not be required to withstand the strain of the sea, and needed only to be put together with flat bottoms and sides. With so large a number of men they could hew down trees of suitable size, and thin them down until they obtained a plank from each. They would then be fastened together by strong pegs and dried moss driven in between the crevices. Pitch, however, would be required to stop up the seams, and of this they had none.

"Then," Beric said, "we must make some pitch. There is no great difficulty about that. There are plenty of fir trees growing near the edges of the swamps, and from the roots of these we can get tar."