My dog knows that doorknobs turn, and he tries to use his paws to turn them. His paws are too dry to have any friction and he doesn't have an opposable thumb so it doesn't work too well, but he clearly understands that the humans turn this thing to get through the door.
In Europe a lot of animals go in and out freely because people have levers rather than knobs on their doors.
I have also had horses who knew quite well how to use their very mobile lips to open stall doorlatches and feed-room door latches. We had a young mare who, when she heard the stable phone ringing next to her stall, would reach out her long neck and knock the receiver off the hook. The caller would be very perplexed at the noises he heard then.
Just because animals don't speak English doesn't mean they don't understand a lot and aren't intelligent.
I have a horse that can untie knots and open certain types of latches.