The coding pin can replace one or more mounting bolts in rectangular connectors. For rectangular connector inserts, the key pin replaces one or more fastening screws. This enables simple coding. In rectangular connector inserts, the guide pin replaces the fastening screws on one side and on the other side the guide socket replaces the screw. This enables a lot of coding possibilities. Also the connector gets a perfect guiding and prevents a skew mating With these inserts, the H-A 3/H-A 4 Code pin is pressed into a socket contact. The corresponding pin contact is removed, meaning one electrical contact will be lost.