Dean,
I have helped build a couple of climbing walls, and built my own up the back side of a town house once.We had another one in the dinning room for a while. This was before store bought climbing walls existed so we had to make our own. Your right the store bought hand holds are big bucks. There are several ways around that.

The cheapest way is just to use small blocks of wood that are quickly sanded to give different profiles. They don't look like rocks but the slants and angles are pretty close to what ya find when your on the pitch. Yeah it may not look as good and pro as the store bought stuff, but it actually provides a good simulation.

2) One ofthe most common ways to build nubbins and hand holds was to take thin pieces of wood and layer them on top of each other like you would a visual representation of a topographic map. Then sand it down. I used to like doing it this way. best It really worked well. and was a good evening hobby.

Another way is to use autobody filler with fibers mixed in then poured into sand moulds. You take a shoe box Fill it with moist sand, sculpt the sand into the shape you want. Then pour in the filler. When you pull it out you have a sand covering that can simulate rock. I recommend fine sand as it leaves a thinner coat. Where the thicker grain stuff goes a few layers thicker and doesn't have the staying power.

Some climbers used mixes of filler and sandand sculpted them, but I found it only worked on small pieces and had a tendancy to crumble.
Belay on

!RUSS

As for connecting them to use at least two bolts with hex nuts instead of one that is rated for outdoor use.