I am building a diorama for my 1/72nd scale M901 hammerhead and it will be presented in a setting that deplicts it being worked on in the company shop. My question to all of you is, the rafters that are high above them, are they I beams or are they the ones that have the cross members attacted to them in that XXXXX pattern?

Jody,
All the motorpools I have worked in for the last 15 years have been I beam.