Abstract: A modular rail as a wire harness mounting system uses clips and tie straps. Each clip has a clip post engaging a mounting hole and a clip head. The modular rail has a plurality of rail segments sequentially joined by toolless interlocks disposed at each longitudinal end of each rail segment. Each rail segment has a plurality of eyelets at longitudinally-spaced locations for receiving respective tie-down straps adapted to encircle the wire harness. The interlocks have complementary clasp features including a latch tab that deflects to enable engagement of each respective interlock. A bottom surface of each rail segment has a plurality of longitudinally-spaced brackets, each having a slide track configured to secure a clip head along a range of locations on the slide track. A top surface of each rail segment receives the wire harness when the wire harness is secured via the tie-down straps being inserted through respective eyelets.