Construction girder (1-4)
I believe the answer is:
i-beam
'construction girder' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for i-beam that I've seen before include "Common type of metal girder" , "Metal girder I-shaped in cross-section" , "Structural girder" , "Rigid metal girder" .)