The barracks consist of two levels , with rifle firing holes on all sides . Iron shutters closed on the inside and was locked with wooden beams . In 1885 the verandah facing the manning parade was enclosed with wooden shutters to keep the weather out . These shutters was removed during 20th @-@ century restoration work and the verandah returned to original condition . The roof was at first flat timber overlaid by 12 inches ( 30 cm ) of lime concrete . This first roof leaked and an iron roof was added in 1885 . The first floor of the barracks contain the officer 's rooms and troop 's barracks room . Its eastern ( outer ) wall is not flat , incorporating a design feature known as " hornwork " , which open the field of fire from the rifle holes . Some of the firing holes was bricked in during the 1930s ; this have been only partly rectified during restoration .