There are many synonyms for the phrase "customary practice." Some common alternatives include traditional practice, regular habit, standard procedure, conventional behavior, established pattern, and typical routine. Other options include common usage, customary behavior, habitual action, and long-standing tradition. These synonyms all convey the idea of behavior or actions that are regularly followed or expected within a particular culture or group. They suggest that these actions are not necessarily required but are considered normal or common. Whether you use "customary practice" or one of its synonyms, it's clear that there are certain behaviors and actions that are expected in many different situations.