An insert (36) is designed to be incorporated in the composition of a fitting element (24) and to form part of the molding surface (40) of the fitting element, the molding surface comprising at least one intersection (32) of at least a first (42) and a second (44) projecting pattern. The insert comprises a junction (46) which is designed to be joined with a molding element (38) integral with the body (34) of the fitting element, the junction (46) dividing the second pattern (44) into a first (48) and a second (50) part, the insert (36) forming the first pattern (42) and the first part (48) of the second pattern (44), and the molding element (38) forming the second part (50) of the second pattern (44), the junction (46) going away from the intersection (32).