The introduction of strict female enclosure was one of the main interests of the monastic reform movements of the fifteenth century which promulgated the return to a stricter observance. Those who tried to introduce strict enclosure into the convents encountered both enthusiastic assent and violent rejection. This article concentrates on the Dominican interpretation of the concept and practice of enclosure. The concept did not originate in the reform movement. It was the result of an amalgamation of ancient monastic traditions and the Dominican preoccupation with obedience. The author explores the ideas of the Order’s fifth master general, Humbert of Romans, and their transformation by the fifteenth-century reformers. Thus she illustrates how the concept of the reformers was enacted: only meticulous observation of the rules could achieve the aim of the religious life—to create the sacred space within, to make room for the encounter between God and the soul.