Thanks Alan, they are attached via Festool 204871 drawer slides with 1/2" spacing. They're really great and give me individual access to one or a group of tools.
Thanks Jim. A workbench is a very personal thing and after a decade of 2 or 3 different types I know this works best for me.
Hah, cool idea! Besides being dead flat and absolutely zero movement/twisting no matter how hard you push on the side, I designed the bench with 15-series extrusion because with a few fasteners you have quite a bit of modularity.