Would you knock at your neighbor's door and just waltz in?! Then why do it at work...rude people...

Seriously, I'm very blessed to have an office, it's more privacy than I've ever had, but it's a glass door actually and I think people think that I may as well not even have one sometimes...some are more respectful than others. I try to leave my door open at all times unless I absolutely have to, so you'd think that if the door was closed people would get the idea...but I swear it's like to those few, a knock knock and a wave is all that is needed to just barge in. And it's usually something that could wait.