The 1” x 1” Decorative Top Runners are standard on all of our vinyl pergolas. These are hollow, but very heavy duty and include End Caps. The top runners provide more shade, add a little flare to the pergola and also add stability. Standard spacing is 16” on center, but you may choose to add more runners for a more customized look. Assembly is easy, simply attach them to the main runners at the marked intervals to ensure proper placement.