A sliding hold-down clip (1) for connecting a roof panel (52) to a purlin (52) in which a support portion (14) extends from a base (12), the support portion defining a slot (20) with fasteners (34) that connect to a roof-engaging plate (36), the fasteners guiding longitudinal movement of the roof-engaging plate (36) along the slot relative to the clip, a distal end of the plate defining a hook (40) for connecting to edges of adjacent roof panels (52), a pair of opposing wings (46, 48) extending laterally from the roof-engaging plate (36) and angled to conform to an anglation of a side portion of the roof panel, whereby fasteners (58) extending though the roof panel and the wings secure the roof panel to the roof-engaging plate. A method of securing roof panels to purlins is disclosed.