Gutters act as a part of a rainwater drainage management system. Uncontrolled rainwater from the roof can damage your foundation, cause siding and wood rot and encourage interior mold and mildew. Use inside mitered corner to follow the shape of a roofline with an inward 90 degree angle. The mitered corner can be installed to gutter using a slip joint connector on either side. - Amerimax 5 in. Aluminum Inside Miter Corner, White