So I was doing a fairly simple model of a Glock hand gun. I had already applied a mirror modifier to the model, that I had so far (which was the grip). Then I applied the subdivision surface modifier. At the point where the mirrored part of the model and the "real" part of the model met it collapsed inside of itself. Bellow will be a picture of the model. I would really appreciate it if someone could tell me how to fix this so I can get back to working on my model. Also the picture is the bottom part of the grip, it may looks like two smaller grips, they are supposed to form one. But like I said it collapsed in on itself.