This is an unfamiliar piece of hardware to many. It is mounted on the jamb side of a pocket door.
It works like a rocker switch. When pushed in, the other half pops out, physically preventing the door from returning into its pocket. A strike is provided to protect the jamb.
Emergency release is accomplished by drilling a small hole in the door. Any thin object inserted into this hole will push the rocker back to the unlocked position.
Available in 8 finishes. See popup menus below.
Shown below in polished chrome in both locked and unlocked positions.