An index of monks serves to:

This is a long entry, scribbled in the margins. The monk’s vow is to stability (staying put), yet his life is defined by movement of others. The index of a monk always points outward. Every knock on the monastery door is an answered prayer. Hospitality means giving the stranger your best bed, your warmest bread, and your deepest silence. In the monk’s index, "Stranger" is immediately followed by "Christ."