Ha!!!!!!!! Et'! That picture is worth a thousand beams! Here I am imagining shop windows over openings--sorry, Faldage, but I just couldn't help imagining windows over openings--and Et' goes out and fetches a picture--and instead of a pretty little cake shop with a window over some random opening, I see a bunch of joists and beams that look like some carpenter's take on the haunted forest.

However, thank you for the digging and definitions--all! This was great, dxb:

In reply to:

'breastsummer' was used for a supporting beam at around breast height

...because the breast height really brought the image home.
Also, the word 'lintel' rang true since I do look for lintels when I traipse about the countryside here when I inspect vacant tobacco barns and old cabins.