A modular jack assembly includes first and second contact-holding inserts (10, 20) having first and second groups of interengaging elements (11 and 21, 12 and 22) between opposite bottom surfaces thereof. The first and second groups of interengaging elements are configured to interferentially engage the first contact-holding insert (10) with the second contact-holding insert (20) in respective first and second lateral and horizontal positioning directions (A, B). The second lateral and horizontal positioning direction (B) extends at approximately 90 degrees. from the first lateral and horizontal positioning direction (A). This arrangement will result in a reliable and stable positioning of the first contact-holding insert with respect to the second contact-holding insert.