Apparatus for securing adjacent tiers of a retractable bleacher to prevent relative vertical movement between the adjacent tiers when the retractable bleacher is fully extended are described. The retractable bleacher includes a first engagement member that is secured to a first decking tier, a second engagement member secured to a second adjacent decking tier. The first engagement member and the second engagement member are configured and cooperative to prevent relative vertical movement of the second decking tier with respect to the first decking tier when the retractable bleacher is fully extended in the open configuration.