go to home depot and use a window latch for verdical windows. its hard to explain but if you live around one they are in the red box with all the other random latch crap. There are like a half moon with a arm that pulls the window down tight and latches it you can install it at the bottom and top and it will keep the doors tight and locked. try it... link to a picture of it. http://www.homedepot.com search "ives window lock" and you will see a little brass one for 2 bucks..