[Happy Monkey]

The next step was to rout out a lip for the plywood back to rest in. We took out the middle upright and put it back together, then laid it facedown on some pillows and styrpfoam blocks. My dad ran along the inside back wit ha router, and I squared up the corners with a chisel.

As an aside, this view shows the cross section of the joint holding the endcaps on the top, which I illustrated with truly awful ASCII art a few posts back. It also illustrates wh the screw insets were put so deep, and why it would have been difficult to put them in later - screwing into a stepped surface is very difficult.