Through anchor and method of manufacture thereof

A through anchor (10) for a vehicle seat belt (21) has a main body portion (12) made of metal in which is formed an insert-through hole (22) through which the seat belt webbing is inserted. A guide member or piece (24) is assembled to a peripheral edge of the insert-through hole and a covering portion (13) is integrally moulded, together with the piece, at a periphery of the insert-through hole. The piece has a surface (25) around which the webbing is trained. A plurality of grooves (42A, 42B) is formed on the surface to prevent the webbing from slipping laterally under rapid deceleration of the vehicle. The grooves (42A) at least in a region (25A) of the piece that is towards the front of the vehicle and which faces inwardly of the vehicle compartment run along a direction of application of the webbing to a vehicle occupant and are formed so as to smoothly curve towards the rear of the vehicle. A method of manufacturing the through anchor is also disclosed.