QO™ and Square D™, QOU2DTILA, is an accessory part for QOO Low Ampere Circuit breakers. Performed as mechanical interlock attachment can be used to interlock two circuit breakers mounted side-by-side so that only one circuit breaker can be ON at a time. A 1P or 2P circuit breaker can be mounted on the left and interlocked with a 2P or 3P circuit breaker on the right. .