"As it opens and closes won't the wheels pass over these bumps several times before reaching the closed or open position? Seems like that would wear down the contact point between door and building over time. "
"That's assuming you never put more liquid than the bottom reservoir can hold. If you poured that same cup of water twice it wouldn't all drain into the bottom..."
"You can be way less accurate with these nails. I think people don't use this feature because it's extremely hard to hit your target on the first swing, especially if you are trying to place a nail exactly on a measured spot."