The rule of St Benedict clearly shows that enclosure was the principal means by which religious communities sought to protect their vocation from any interference from the outside world: it was enforced by monastic rules and expressed in the monastery architecture. In the preceding chapter, we saw how the laity intruded on sacred space. Enclosure, and the rules and customs governing it, were not just designed to keep lay people out, but also to ensure professed religious remained within their monasteries as far as possible. In this chapter, we shall consider how enclosure worked in practice as against the statutes laid down by monastic rules and the expectation of ecclesiastical visitors like Abbot Stephen and Archbishop Eudes. Monks and nuns temporarily left their cloister for various reasons and some indeed turned apostate and left their monasteries for good. We will also look at the use of monastery buildings, which is necessary for a full understanding of the architectural practice of enclosure. Statutes relating to enclosure also ensured the separation of certain groups from the rest of society; in this context, the attitudes towards those with leprosy and the governance of hospitals have particular relevance.