Cutting Square Hole In a Cylinder I'm trying to model a spot light and couldn't figure out how to cut a perfect hole on the body without having weird artefacts on the mesh. I have been trying to model this thing for months and still stuck in the same point without any progress. hope some one can help. 

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Here is a way to do it, but if you want to avoid any pinching it needs more geometry than on your screenshot. Once done, you can delete the useless geometry, i.e. vertical edge loops on the rest of the cylinder: