The monk Grimlaicus (ca. 900) wrote a rule for those who, like himself, pursued the solitary life within a monastic community. Never leaving their cell yet participating in the liturgical life of the monastery through a window into the church, these enclosed sought to serve God alone. Beyond the details of horarium, reception of newcomers, diet, and clothing, Grimlaicus details practical measures for maintaining spiritual, psychological, and physical health, and for giving counsel to others. Scripture, the Rule of St. Benedict, and the teachings of early ecclesial and monastic writers form the kernel of Grimlaicus's wise and balanced rule, presented here for the first time in English translation.