The Collaborative International Dictionary
Straining piece
Straining \Strain"ing\, a. & n. from Strain.
Straining piece (Arch.), a short piece of timber in a truss, used to maintain the ends of struts or rafters, and keep them from slipping. See Illust. of Queen-post.
Wiktionary
straining piece
n. (context architecture English) A short piece of timber in a truss, used to maintain the ends of struts or rafters and keep them from slipping.