There's no support under the monitor and it's not bolted to the wall. I've glued and screwed two 2.6m long, 16mm thick sheets of marine grade MDF together. Makes for a very sturdy desk.
That's it a P275. I use it to do professional design work, love it. I'll be sad when she dies but then that will give me an excuse to get myself a 30" widescreen! I built the desk to allow room for two of them side by side so space isn't an issue.