badazzTL-S

I went over to my freinds house to see how he was doing over the hoildays....and to show him my new car (07 WDP TL-S). He totally loved the car. He got in and I showed him the features of the car and after about 5 minutes we headed back inside.....as he got out he SLAMMED my the door....I mean the car is only a week old and the last thing I need is a shattered window over winter break!. I did not want to sound like a stuck little kid and say "dam you slammed my door" but I wanted to say something so he knows next time...any suggestions for saying dont slam my door in a well mannered way? Have you ever encountered someone slamming and got tick off?