The present disclosure relates to a retractable tape rule assembly locking system. The system comprises an elongated tape rule blade, a reel, a biasing spring, a stop assembly, a stop surface, a stop assembly locking device, a housing assembly, and/or other components. The stop assembly is configured to selectively engage the elongated tape rule blade to maintain the elongated tape rule blade in the extended position. The stop assembly is configured to be moveable between a default position and an open position by a user. While in the default position, the stop assembly engages the elongated tape rule blade to prevent retraction of the elongated tape rule blade. The stop surface is associated with the reel and configured to engage the stop assembly to prevent rotation of the reel to retract the elongated tape rule blade.