Stuck trying to do "Pull"

I'm learning DSM. Trying to layout some shelves. I got the shelf made, duplicated. Made an Upright. But then the upright stuck. Can't select it to pull it to the right length.

Can't find a property that looks any different from the shelves which do work.

I'll try to add images and a link to the DSM file.

I can select shelf faces. But the gray "Upright" on the right is locked in some way that prevents me from "Pulling" the face to the correct length.

Link to Shelves File

Thanks for your help

wp