replace plastic door panel

Hi I see a few people on here wanting to fit cat flaps. I want to remove one. It is in the panel of a door, looks like plastic. The previous owner ( I just moved into house) has kept the original door panel, so he reckons the panel with the cat flap in it can be removed and the original panel without a cat flap put back in. It's not obvious how to do this - there is some sort of rubbery-looking seal strip say 1/4 inch, then a bevel strip say 1/2 inch, surrounding the panel. Anyone know how these doors fit together please? I don't want to break anything. TIA, Terry

If the removable beading is on the outside of the door I would say you need to remove the internal rubber then take the beading out. Don't forget to toe and heal the new panel

Ah thanks. Do you mean the outside of the door as outside the house ? Also I don't know what toe and heel means ! Any advice please? Ta, Terry

Ah, got same thing inside and outside looks like, sort of rubber/plastic seal then bevel-Terry