Here's a good shot showing both connecting plates fastened to the 1/2" thick inner extensions. You can also see the C clamps that hold the ends of my treads together. On the right you can see the screw heads that fasten the knee plate to the inner extensions. These screws will be completely hidden by the knee.

Here they are with treads and side panels in place. I still need to put on the dummy soil sampler door. The finish looks a little irregular with the flash. It looks much better in room light. Thank god I won't be displaying it under flourescent lights. Ahhhhhh . . . mood lighting . . . works every time!