X-rays girders (10)

I believe the answer is:

crossbeams

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'girders' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps there's a link between them I don't understand?

'x-rays' is the wordplay.
'x' becomes 'cross' (I've seen this before).
'rays' becomes 'beams' ('beam' can be a synonym of 'ray').
'cross'+'beams'='CROSSBEAMS'

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I've seen this clue in The Guardian.

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