A ring mechanism for retaining loose-leaf pages comprises a housing, hinge plates, and ring members. The housing supports the hinge plates for pivoting motion relative to the housing to open and close ring members mounted thereon. The mechanism comprises a thin, flat travel bar below the hinge plates arranged in a vertical orientation. The travel bar is supported by coil springs in a position where the travel bar is adjacent a bottom surface of the hinge plates. The travel bar moves relative to the hinge plates between a position blocking the hinge plates against pivoting when the ring members are closed and a position allowing the hinge plates to pivot when it is desired to open the ring members.