135 Degree Gutter Angles, or 45 angles as they sometimes referred to as, are generally used when the guttering and fascia runs above a bay window.  As the system is symmetrical, both internal and external corners use the same fitting - there is no difference.You should always support any 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.