Abstract: Systems and methods are provided for interfacing to a guide rail. Provided is an improved rail interface wheel is provided including a continuous U-channel formed about a periphery of a puck shaped wheel body. The rail interface wheel is configured to spin about a spin axis. The U-channel includes a primary diameter measured parallel to the spin axis and a secondary diameter measured along a line that is coplanar with but not parallel to the spin axis. The secondary diameter is preferably at least as great as the primary diameter. The rail interface wheel may be used in combination with a movable structure, such as a library ladder.