What is the metal bar in this picture specifically named?

[MAXOFLIFE]

Sorry for a such a simple question, but one of the biggest hurdles my team has to worry about is specific names for mechanical and electrical components when we can't find a serial number or something similar.

What are the beams that are holding these two tread's together called? We ordered a set of treads from AndyMark and want to have everything we need to set them up when they arrive.

(Edit: Image was too big)
It's the picture under the More category.
http://www.andymark.com/Rhino-p/am-3322.htm

Thank you for your time and help! Is there a better forum to ask questions like this on for future reference?