When I notice 2 edges in each other, I select both of the points and hit Alt+M, which allows me to merge them. I always merge them at center to have both points merge and have them as one point. I always, when I finish a model, select every edge in wireframe mode twice to see if there are edges in each other that I may have modeled by mistake. Is there any way the system could help me with this task? It takes a lot of time and I could always miss something. Any help is appreciated. Thank you!