A member of a kind of roof truss (a hammer-beam truss), so framed as not to have a tiebeam at the top of the wall. Each principal has two hammer beams, which occupy the situation, and to some extent serve the purpose, of a tiebeam.
summer (tree)
How often have the words hammer beam and summer (tree) occurred in a corpus of books? (source: Google Ngram Viewer )