A tonneau cover cargo containment track rail system including a cargo hold down and at least one tonneau cover rail. The cargo hold down has a base portion and a handle portion. The handle portion is operably attached to the base portion for movement between an engaged position and a disengaged position. The tonneau cover rail has a first attachment mechanism attached thereto. The first attachment mechanism is adapted to receive a portion of the cargo hold down to retain the cargo hold down in engagement with the tonneau cover rail while permitting the cargo hold down to move with respect to the tonneau cover rail.