naturally shaped branches

they were formed of naturally shaped oak trunks, I believe, Helen. The key fact about the ones I have seen is that this structure supports the roof directly from the ground, not built up off the walls,

Here’s a pic of a typical barn showing the massive and curved A-frames:
http://www.rogersavage.co.uk/cruckbarn/

Leigh in Worcestershire is said to have the grandest one in the UK, though I have only heard about that – it sounds stunning.

btw, the bits you were referring to in the construction of ships are called knees - isn't that perfectly expressive of the turn from the ship's hull to its deck?!