In reply to SimonMarcYoung:
For a woody the best thickness to use is 18mm I'm pretty sure. On mine I used marine ply, although that won't be necessary for yours since yours will be indoors I'm presuming?
You can get M10 T-nuts that you just hammer into the back of the board very cheaply online, drill a 13mm hole in the back and hammer them in. These will then accept 10mm bolts to wack the holds up.
The moon site has a pretty good guide for how to build a decent board and the various supports needed. The pdf is here:
http://www.moonclimbing.com/moonboard/downloads/MoonBoard.pdf
Hope this is helpful