1. Arch. A horizontal beam connecting a pair of rafters, which prevents them from spreading or ‘sagging’ (bending in); it is attached about the middle of the rafters, which distinguishes it from a tie-beam.
1659. T. Willsford, Archit., 12. Principall sparres or rafters … are made according to the true pitch of the building intended; about the middle in common structures, each of them hath a collar-beam.
1663. Gerbier, Counsel, 73. The Coller beams eight and three inches.
1667. Primatt, City & C. Build., 86. Choller-beams.
1837. P. Nicholson, Pract. Build., I. 29. A collar-beam is … usually employed where there are no king-posts.
2. Naut. (See quots.)
1769. Falconer, Dict. Marine (1789), Clef de beaupré … the collar-beam, which is raised a little above the second deck, to fortify the bowsprit.
c. 1850. Rudim. Navig. (Weale), 95. The Collar-Beam is the beam upon which the stanchions of the beak-head bulk-head stand.
