a first connecting element and a second connecting element, each connecting element being fixedly positioned on the structure, wherein the pivotable member is pivotally coupled to the first connecting element;

a rod having a first segment and a second segment, the two segments rotatably coupled together at a first end of the first segment and a first end of the second segment, wherein the first segment is rotatably coupled to the second connecting element at a generally opposing second end of the first segment, and wherein the second segment is rotatably coupled to the pivotable member at a generally opposing second end of the second segment;

a locking device adapted to selectively fix the first segment and the second connecting element with respect to each other such that a pivoting motion between the first segment and the second connecting element is inhibited, wherein the locking device comprises:

a slide member slidably positioned proximate the second end of the first segment of the rod, the slide member including a stop fixedly positioned with respect to the slide member, the stop defining a protuberance,

a biasing device adapted to bias the slide member for slidable movement along the first segment toward a contour of the second connecting element, and

a notch defined by the contour of the second connecting element,

wherein the slide member moves along the contour of the second connecting element as the first segment pivots with respect to the second connecting element, and wherein the stop is releasably received in the notch thereby inhibiting the pivoting motion between the first segment and the second connecting element, and wherein the stop is disengaged from the notch by slidable movement of the slide member away from the second connecting element thereby allowing movement of the slide member along the contour of the second connecting element and pivoting motion between the first segment and the second connecting element.