The P&W-RR is designed as a fold-up layout. This provides a space-saving benefit by allowing you to store the layout in a minimum of space when its not in use. The shelf area is a stable location for trains between operating sessions as the remainder of the layout would be folded up on end when not in use and needs to be cleared of trains before raising it up.
The bench-work is made with 5/8" plywood and a structure of 1"x2" boards. After adding more boards on top to support the scenery backdrop (that will split the layout for two-sided viewing), I will determine if more structure is needed below to maintain a stable working surface. Since a foam base will be used for all of the layout features, the relatively lightweight structure should be adequate for this design. After the layout design is transferred to the table, some of the plywood material will be cut out to reduce the weight and provide access holes to hidden sections of track.
In my implementation, I started with building a shelf that locks onto a support structure attached to the wall. After framing the rest of the layout and adding hinge blocks, the hinges were installed to connect the main table to the shelf. In the second photo you can see the white shelf with the left-side locking feature and one of the hinge structures. By unlocking the shelf from the wall, the whole layout can be removed and I intend on making a separate base to allow me to make the layout a standalone design given I want to take it on the road!:o)