How do you remove the rear seat backs?
 

Hopefully the easiest question I've asked here but...

My rear seat backs seem to have lost their pull knob assembly that allows them to either flop down or lock in the upright position. I took a pretty Quick Look at it but I don't see what is missing or how I can fix it. One seat is down and won't stay up, one seat is up with no visible way to tip down.
I assume by removing them, the apparatus will be evident and I can figure it out?
Are they all the same? Mine is a 1986.