The vow of enclosure is a religious vow taken by some Poor Clare sisters in addition to the three ordinary vows of religion: obedience, poverty and chastity.
Description
When a Poor Clare takes this vow, she may not leave the monastery except for doctor's appointments, civil duties, or emergencies. Some sisters, known as 'externs' do not take this vow and are therefore able to leave the building to do charitable works.
The Poor Clare Nuns constitute the second branch of the Franciscan Order, founded in the thirteenth century by St. Clare under the inspiration of St. Francis of Assisi.
References
Vow of Enclosure Wikipedia(Text) CC BY-SA