A retractable tape rule assembly locking system, the system comprising: an elongated tape rule blade configured for measurement, the elongated tape rule blade including measurement indicia; a reel configured to retract the elongated tape rule blade from an extended position to a wound position; a spring configured to apply a rotational bias to the reel that rotates the reel to retract the elongated tape rule blade into the wound position; a stop assembly configured to selectively engage the elongated tape rule blade to maintain the elongated tape rule blade in the extended position or the wound position, the stop assembly configured to be moveable between a default position and an open position by a user, wherein, while the stop assembly is in the default position, the stop assembly engages the elongated tape rule blade to prevent retraction of the elongated tape rule blade, and wherein, while the stop assembly is in the open position, the stop assembly is disengaged from the elongated tape rule blade to allow retraction and extension of the elongated tape rule blade; a stop surface associated with the reel characterized in that the stop surface is configured to engage the stop assembly to prevent rotation of the reel to retract the elongated tape rule blade when the stop assembly is in the default position and a diameter of the elongated tape rule blade wound on the reel is less than a pre-determined diameter of the elongated tape rule blade wound on the reel; and a housing assembly configured to house one or more of the reel, the spring, or at least a portion of the elongated tape rule blade. an elongated tape rule blade configured for measurement, the elongated tape rule blade including measurement indicia; a reel configured to retract the elongated tape rule blade from an extended position to a wound position; a spring configured to apply a rotational bias to the reel that rotates the reel to retract the elongated tape rule blade into the wound position; a stop assembly configured to selectively engage the elongated tape rule blade to maintain the elongated tape rule blade in the extended position or the wound position, the stop assembly configured to be moveable between a default position and an open position by a user, wherein, while the stop assembly is in the default position, the stop assembly engages the elongated tape rule blade to prevent retraction of the elongated tape rule blade, and wherein, while the stop assembly is in the open position, the stop assembly is disengaged from the elongated tape rule blade to allow retraction and extension of the elongated tape rule blade; wherein, while the stop assembly is in the default position, the stop assembly engages the elongated tape rule blade to prevent retraction of the elongated tape rule blade, and wherein, while the stop assembly is in the open position, the stop assembly is disengaged from the elongated tape rule blade to allow retraction and extension of the elongated tape rule blade; a stop surface associated with the reel characterized in that the stop surface is configured to engage the stop assembly to prevent rotation of the reel to retract the elongated tape rule blade when the stop assembly is in the default position and a diameter of the elongated tape rule blade wound on the reel is less than a pre-determined diameter of the elongated tape rule blade wound on the reel; and a housing assembly configured to house one or more of the reel, the spring, or at least a portion of the elongated tape rule blade.