We're building a new house and have some big (expensive) sliding doors that we don't want our golden retrievers to scratch up when they want to go outside. I need suggestions for inside and outside.

We may have to put up more fences outside to keep them off the porch (there's another side door they could enter- and likely scratch up). Inside though, I'm not sure what to do. I currently have some small, thick plastic on the door outside at our current home, but that's just not feasible for these big sliders (and would look horrible). We may have to work on training them to ring a bell or something, but my dogs are 5 and 6 and historically have not trained well. One almost flunked puppy school and a two week stint a few years ago showed almost no change in either of their walking habits. Any thoughts?