Installing the dog door

I had to install a dog door for Monty so he can come and go as he pleases.So we went out in search of a dog door.Finally found a half decent one and we made the purchase.Once home I installed the dog door(which was a bit of a pain to install).ONE PROBLEM.Oscar could fit through the door.The door was for medium dogs and Oscar is a large labrador. So I had to think of another solution. I had to make a gate outside the dog door which was big enough so Monty could get through and Oscar could not. I then proceeded to measure the size of Monty so he could just fit through. It took Monty a bit of time but he worked out how to use the dog door and now uses it all the time.Oscar now has to watch Monty go in and out of the house as he pleases. Oscar is an outside dog but he is a happy dog and I think he enjoys the extended family.