They built their ships from the outside in with axes, block planes and augers.
Laid up the hull (held it together with thousands of long iron rivets) first and then put the ribs in.
Wouldn't use saws. Split the tree into planks with mallets and wedges where it fell, thicknessed them with axes and finished off the high spots with block planes.
Guy who captained a reproduction of the Gokstad crossing the Atlantic a century ago said it scared him bad till he got used to it. The way it was flexing had him thinking it was going to fall apart. But that was the idea. Flex over the waves rather than crash through them.
I've got a few pics of the solution they used to tighten the mast stays (since they didn't use the block and tackle) I've got to dig up and post.
Brilliant. No moving parts and one man, two at most, could handle the job.
