§ 30. The result of these common requirements was the general prevalence of the cruciform plan in churches of monks and canons. The eastern arm contained the high altar and presbytery. The quire occupied the crossing of the transepts and one or more of the eastern bays of the nave. The transepts were provided with eastern chapels, and in the transept next the cloister direct access was given to the dorter by the night-stair, which was used by the convent in going to and returning from the night office of matins and lauds. The quire was separated from the rest of the nave by a stone screen with a loft above, known as the _pulpitum_, a bay west of which came another screen, the rood-screen. The nave usually had north and south aisles. In the aisle-wall next the cloister were two doorways, one opening into the east, the other into the west walk of the cloister. The Sunday procession left the church by the eastern doorway, which was also the entrance used by the convent for the day offices, and returned by the western. There was frequently a tower above the crossing, and the larger churches had additional towers at the west end of the aisles. Even Cistercian churches, in defiance of the statutes, succumbed in the later middle ages to the attractions of tower-building. A tower was built above the crossing at Kirkstall and at the west end of the nave at Furness. At Fountains, after a futile attempt to build above the crossing, the tower was added to the end of the north transept.