A more thorough explanation:

A customary tenant is a person who holds land or tenements by the custom of the manor. Over time, customary tenants became known as copyhold tenants. They hold according to the custom of the manor and have fairly definite terms.

For example, in the feudal system, a tenant in villeinage appears as no mere tenant at will, but as holding permanently, often heritably, on fairly definite terms. He is a customary tenant, customarius, consuetudinarius; he holds according to the custom of the manor.

Another example is that a tenant in a copyhold estate holds the land according to the customs of the manor. The copyhold tenant is a customary tenant who holds land by copy of the court roll.

These examples illustrate how a customary tenant holds land according to the customs of the manor and has fairly definite terms.