I remember when I first started using a router to cut out windows on a new construction project and every time I would just go the wrong way. It didn't matter how many times they said you got to go this way. It always felt like I had to go the opposite way. But anyway, after you're done cutting out the window you can always clean it up a little bit. As you can clearly see here! But using a router to cut out Windows is a great idea compared to using something like a sawzall. But everyone's got th