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 external corner, the corner goes away from you out of sight. External corners are usually used on all 90 changes of direction except at the foot of a valley, where you would use an internal corner.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.