Heavy Suspension System: Heavy Steel Flat bar with a eye-nut protruding from underneath extrusion. Must be used in perimeter extrusions for 3 Season Pergolas or any Frame Beam for the 4-Season Pergolas. Each eye-nut is for hanging one end of Hammock or Swing. An egg-shaped swing can be held with one eye-nut, though not exceeding 200lbs.