what is a "DF-2" boxcar?

As a boy I always liked the American Flyer green boxcar with the yellow band that said 'DF'.  I didn't realize what it meant until just now!

DF stood for "dunnage free".  This was a system cross bars that hooked into angles that ran the length of the car, maybe one foot apart. The angles had lots of holes in them and the cross bars had vertical pins to engage the holes.  DF2 was an improved system where there were channels the size of the siding boards so they did not protrude into the interior of the car. The channels had lots of holes drilled in them.  The pins in the DB bars were horizontal.  The DF bars had a jacking mechanism built into so the bars could get longer to engage the pins on both sides of the car. DFB cars got rid of the cross members, which were always getting left behind at the unloading site, and put in two moving bulkheads, which ran on a track that ran down each side of the car near the ceiling. The bulkheads would be moved to one end of the car while the other end was being loaded. Then one bulkhead would be locked against the load.  After the other end was loaded, the second bulkhead would be locked in place. Then the doorway area could be loaded, but it usually required some conventional dunnage to fill in any gap. All the systems were abused by the shippers and were expensive to maintain. 

I believe these cars were mostly used for LCL shipments.

In the Sacramento Valley the WP and SP used these cars by the thousands to ship can goods east.

can anyone find a photo of how the system looks?  thanks

Hobos of the day used to really like these cars, as they each had their own seperate 'room' for the ride.