Abstract: A clip for slidably attaching a ribbed metal roof panel to a structural support underlying the roof panel includes a base member and a slide member which are interfitted in a manner which permits tile slide member to shift relative to the base member. The base and slide members include interfitted sections which are U-shaped in cross section, and the interfitted sections include a cutout and detent which cooperate to limit the amount of relative shifting between the base and slide members. A particular embodiment of the clip is well-suited for use when mounting a ribbed panel in spaced relationship above a ribbed panel of an existing roof structure.