Steel Cabinet Bar

Steel Cabinet Bar
15 "File cabinet drawers, ah! How it works

I had a 15 'wide with 12 "drawers, then May upgrade to a drawer. It turns out that this is one of 18 "with 15" drawers. I can not find how to use it! During the search, does not seem to hanging folders come in any other size 12 ", so I'm missing something? Please link if you found anywhere that sells a way to use (or folders what is needed to connect steel bars). Thanks! ... Or tell me I lost my money because this type of container file is used otherwise. : (Okay, there seems to legal-size folders. I guess this is the answer I was seeking.

Yes, a legal-sized cabinet.