Abstract: A mounting system for plastic siding comprises an elongated nailing strip from which a siding panel is suspended by means of interlocking channels which permit longitudinal relative movement resulting from differential thermal expansion or contraction. A predetermined amount of horizontal overlap of adjacent panels is assured by the provision of a notch adjacent each end of the panel, which notch is intended to be vertically aligned with the end of the adjacent panel. The same notches provide a guide for centering the nailing strip on its associated panel. Unintended disassembly of each strip-panel pair is presented by dimple-like deformations near the end of each strip cahnnel, which function to limit the longitudinal travel of the associated panel channel therein.