I've seen the following example sentence for one of the meanings of strut, "Brace (something) with a strut or struts.":
the holes were close-boarded and strutted
The sentence is from Oxford dictionaries
(EDIT: ...and without any further context.)
I haven't found close-boarded or close-board in any dictionary. I have found, however, the term "close board fencing". Does close-boarded mean here that close board fences were put up around the holes (and generally mean "to put up a close board fence")?