Hmm, I'd say you can get those bars off with no check required. You could do an individual check, but I figured everyone was working together to assist in the ulitimate scavenging and construction check by whomever is going to be primary for building it.
Most logical way I think that would play out is individuals contributing parts to the primary for them to assess and assemble into a stretcher. Anyone assisting gives a harmony bonus, plus potental tools bonus for the materials. The final check would be to determine whether or not the stretcher is any good.
To be honest, I probably should insist on the individual check, but I'm being kinda lazy today, and don't want to clutter the flow of posting with too many incidental dice rolls