What does this mean?

Why do some websites call a Middle Atlantic rack "MIDDLE ATLANTIC SLIM5 KNOCKDOWN 37-SPACE, 26"DEEP RACK"
What does the Knockdown part mean? Is there something different about a rack that says knockdown in the description and one that doesnt have that in the description?
Does that just mean the rack comes unassembled?
I am ready to pull the trigger on a Slim 5 -37-26 rack and I dont want to order the wrong rack.

Thanks for your replies in advance!

Sling.
Edited by Slingblayde - 10/4/12 at 3:15am

Thank you jautor, thats what I was hoping it meant.