low-end alternatives to a slider

• jigs that allow a camera to slide along a wire or rope, AKA a "cable cam":
  • Wiral
  • Cinemotion
  • Proaim
  • jury-rigged from the "Tin Can Cable Car" [buy]
  • jury-rigged
  • jury-rigged, though fairly high-end for being jury-rigged
  • well-engineered by an individual