The Avant Banister Kit allows for the 5-12501 KiddyGuard gate to be mounted onto a stairway banister. Minimum size of 7/16", maximum of 2" square or round post. The "Locking Side" kit contains the hardware needed for connecting the Locking Strip of the gate to a stair banister. Use the separate "Housing Side" kit for the opposite side if needed. Choose Black or White color to match your gate.