It holds the fender and I think it's welded on, not bolted. The nicest thing I've seen done is bolting a chrome oval luggage rack to it. I think it's a standard piece from NField Gear and/or Hitchcock's for an older bike. It bolts up, looks good and is functional, and the shiny chrome makes the ugly subframe largely fade away into the background. Sorry I don't have the specifics, I'm sure someone will chime in.
Scott