I'm going to fit a cat flap in a brick wall. My intention is to drill out a square hole through the wall. Then create a wooden (MDF) tunnel to fit inside this. On one end of the tunnel, I will attach an extra piece of wood with the cat flap fitted.
My question is this How do I secure that wooden tunnel into the brick-work?
Obviously the drilling is going to leave a messy edge, which I intend to tidy up with cement and/or filler, but I can't see that these are going to get much purchase on the MDF. I can imagine, one good kick to the outer face would send the whole structure flying into the house.