An "emergency" stop (valve) that is usually installed before the water supply line (below) to toilets and faucets. Angle stops are to be shut off in case of an emergency or repair and are generally not designed for daily on and off useage. The difference between a "straight stop" and an "angle stops" is that the "angle" stop changes direction by 90 degrees while a straight stop is like most valves and does not change direction.