What’s the most common mistake when choosing a dog door? The most common mistakes are probably getting a door that’s much bigger than the pet needs, and buying the cheapest door possible. A flap door that’s much larger than the pet needs can be difficult to open, because the flap becomes too heavy. It also creates a much larger hole into the house than necessary. The bigger the pet door you get, the more important it is to choose a high quality door. Top of the line doors will open easily even if they’re big, and keep weather outside. Buying the cheapest door on the market might seem like a great idea at the time, but pet doors are a long-term investment. If someone were to install a new window in their house, they would probably research and choose carefully; there are many types of windows. The same is true for pet doors. Choosing a higher quality door may mean paying more upfront, but it also means less maintenance, fewer problems, and less impact on the indoor climate.