90 Degree Gutter Angles are used to turn the gutter around the corner of a building. As the ogee system is not symmetrical, internal and external corners are different fittings.The product image clarifies the difference but essentially if you are stood in front of an internal corner, the corner comes towards you - on an external corner it goes away from you. Internal corners are most commonly found at the bottom of a valley on a roof.You should always support a gutter angle by positioning a fascia bracket within 150mm on both sides of the angle. This will prevent the fitting from sagging when it is weighed down by water or snow.