An automatic gain control device of an optical fiber amplifier that outputs a compensation signal to control a gain value of the optical fiber amplifier is disclosed. The slurry is made from a hydraulically-active cementitious material, a suspending agent, and, as a retarder, boric acid. Engagement of the bicycle wheel with the base members prevents the bicycle wheel from rolling, to maintain the bicycle in engagement with the support. Additional building elements, such as pre-fabricated walls may be attached at the connection points.