What a coincidence, I made my own wobble board yesterday. Glue should be dry now so I'll varnish it and find a non slip top for it today.

I'm getting back after a replacement knee and seeing a physio. Now that I have a reasonable range of movement and the strength is coming back she advised balancing on an unstable surface to build leg and core strength. A thick cushion is the cheap and not very good option, a wobble board is best.

However when I said we had one (though its currently out on loan) she asked what type and its the round platform type with the hemispherical ball underneath to make it wobble. She said that's the advanced one and she's right, its really difficult; when we got it (10 yr ago, me with knee cartilige debridement and Sue with ACL reconstruction) neither of us could balance on it and despite Sue's yoga, she still can't.

The recommendation while in recovery mode was I use the seesaw type that only rocks in one dimension. One small sheet of 18mm ply later and I was well on the way. I wouldn't be able to make a hemispherical one any way, I don't have access to a wood turning lathe.

Actually, I needed 2 sheets of ply. I cut the platform from the 1st sheet and discovered it was full of voids. Took the wood back to homebase and delaminated it in front of the sales assistant. Out of 11 sheets they had in stock I rejected 8 on examination before settling on one I thought would be OK. I'll probably still have to sheath the bearing surfaces of the rocker sections though I never realised modern plywood could be so rubbish,