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Extra Heavy Duty Cable Drum Roller Rail (Pair) - Midland Site Supplies
2PCS YUEBM Track Roller Wheels Accessory Parts of The Beam Trolley System Used with Box Rail Strut Channel to Mount Heavy Barn or Shed Sliding Doors: Amazon.com: Industrial & Scientific
Pallet rail - that is the way they work
Roller rail guides: Three reasons why you should use them