Tank sorry I didn't see this sooner.
COngrats on your Jayco 21J, we absolutely love ours!
The 21J has fold out beds on the front and street side. They are connected via cables that run from the top edge of the door/bed into the bulkhead wall and are rated for about 1000 lbs.
To keep the canvas taut there is a shepherds pole that will connect to the upsidedown "U" shaped bar that runs around the window at the edge of the bed.
The link below is one of the poles I'm talking about. The end you see is the one that goes inside the camper above the bed, the other end is straight.
Supposedly you can only find parts from a Jayco dealer or from 1-800-rvjayco They want the VIN when you order parts.