A clip assembly secures standing seam skylight or roofing panels to substrates and allows for a full range of movements by the panels while eliminating or reducing frictional noises. The clip assembly may also be used with wall panel systems. The clip assembly includes a first clip member and a second clip member each having an upright member and an upper flange member and a lower flange member extending therefrom. The assembly further includes a gap formed between the upright member of the first clip member and the upright member of the second clip member. In one aspect the clip assembly includes a base which allows the assembly to slide.