Grace Frame - end cap locking mechanism assistance needed
 

Hello,
I have accidentally pulled too hard on the end cap that locks/unlocks the rail on my long arm frame. The end cap piece came right out. I did this once before, a long time ago, and can't remember how I got it back into place.
I have a Grace frame but I can't remember exactly which one it is. It's about 5 years old.
Any one here recall how to re-insert the end cap piece?
I've looked at the website for The Grace Company but there isn't anything there that was helpful.
Any assistance welcome, thanks,