QO and QOB one, two and three pole thermal magnetic circuit breakers provide overcurrent protection and switching on ac and dc systems. These circuit breakers have an over center, trip-free toggle mechanism with quick-make, quick break action and positive handle indication A full line of factory installed accessories, such as shunt trips, auxiliary switches and alarm switches, is also available This attachment is for padlocking 1P QO circuit breaker in OFF position only, fixed attachment.