Here's a detail, from the back, of the panel that moves up and down revealing the TV. The frame around the panel keeps it square/flat and also prevents it from moving horizontally, even when it's positioned above the TV. The bottom edge of the panel will always be in front of the top bezel of the TV, ensuring that it comes down in front of the TV and not on top of it, getting stuck.

The panel is attached to the roller via high-strength woven cord that's set at a slight angle. This will allow the cord to roll around the roller without rolling onto itself. There will probably be only a single cord that goes from one end of the roller, comes down into the panel frame and then back up to the other end of the roller. This should make it easier to set the panel level without having to keep playing with cord length.