I'm looking for some suggestions here. My two outdoor dogs live in a large fenced run when I'm not home to give them the freedom of the yard. They have access to a semi-heated shack, within which they have the choice of either a heated doghouse or an unheated one, both big enough for both dogs. I have tried all sorts of "dog-door" devices for the opening by which they enter the shed. I am trying to cover the door to improve the efficiency of the heating, as a lot of heat is obviously (and expensively!) going right out that open door.

Here's my problem: One dog is fearless, inquisitive, and would probably be able to operate a combination padlock and a sliding metal door if I used one . The other, however, is timid and shies away from anything that I place over that door. Swinging dog-doors are out of the question...she simply will not use them. I've hung pieces of heavy blanket over the door, and these are of course chewed and destroyed within 24 hours. I tried strips of a heavy rubberized material, and while they worked they also were soon destroyed.

Can anyone suggest anything that might work for this purpose. My wife and I are planning to retire and move to a much colder region in the near future, and I really need to get this project to work somehow before that happens. Thanks for your time and for any suggestions.

John