Metalworker's union

I think it could be either:

Which length description are you looking for?:

solder

(Other definitions for solder that I've seen before include "Join or fuse metal, using an alloy" , "Join two metals with a melted alloy" , "Metal bond" , "Soft alloy used to cement metals" , "Join two metal surfaces together" .)

I've seen this clue in The New York Times.

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