Stanley can get further and further back every day - today he's been running round the garden with my wooden spoon like its the greatest thing he's ever had in his life. He's also figured out that when I put him outside (if he's done something on the kitchen floor I need to clean up, like pull the bin over) that he needs to jump up and pull the handle down and he can get back in. Far too clever that puppydog.
A friend's Lab used to do this. So they turned the handles over so you needed to pull them up to open. He worked that out, too