As agricultural outbuilding, coops are easily discernable from other farm buildings because they are typically longer and lower in profile. Their roof shape also distinguishes them; most coops have either a shed roof or a partial gable (or saltbox-type) roof, with the front slope of the roof descending only about halfway down. Underneath the front eaves is long bank of window openings (commonly covered with chicken wire) that usually extends nearly the full length of the building. Larger coops may vary from this plan, sometimes being wider with a full gable roof and open sides. Early coops were typically constructed of wood planks; however, by the 20th century cinder and concrete blocks became increasingly popular.