Wallplates in recess

[crazylarry]

Hello. I have a hole in the chimney stack through which I'm running some AV wires. The wires come through holes in the other side of the stack from the outside. On the inside is a brick-sized hole.

I want to mount wallplates in this hole. I've tried mounting the 25mm back boxes onto a brick to fix inside the hole, but it is proving too difficult to get aa the wallplates aligned with each other so that they are level.

What is the best way to do it?

 

[redpis]

Timer backing and dual back box maybe?

http://www.tlc-direct.co.uk/Images/Products/size_3/AP636.JPG

 

[crazylarry]

That looks pretty good, thanks for that suggestion. I'm not sure if the middle section is wide enough to accommodate the wallplates though. If it's 3/4 inch then it will be OK. So I guess I'll have to try and find out.