Any kind of internal overhang could work if the dogs aren't too intent and too determined to tear it down. Some dogs will keep jumping on it until they hurt themselves or dismantle it! But most lab type dogs aren't that emphatic about wanting to get out. Some larger terriers and poodles and certain herders and those types can keep at an overhang until they injured their mouths, paws.
__________________  Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |