I would like to fit a cat flat into a replacement upvc panel but don't know the thickness of my current panel. How do I find this out and does the new panel have to be of the same thickness??

Paul, July 2009

Place two wooden battens parallel across the door, with it open and the battens extending beyond the door - you may need help. Measure the distance between the battens. You now have the thickness of the door.

Place a batten across the face of the door where the panel is and measure the distance from the batten to the panel. Do the same on the other side of the door. Add these two together and deduct from the first measurement.

You now have the thickness of the panel.

Yes it will be best if the new panel is the same thickness as the original - fitting will be much easier.

I'm led to believe that Isaac Newton invented the cat door when he was 12 to avoid the bother of letting the cat in.

Peccavi, July 2009