Blackburn Interlock Seatpost Rack. Jim Blackburn virtually invented the aluminum rod rack in 1977. It's what put Blackburn on the map. The company uses aircraft grade aluminum, the finest mounting hardware and thoughtful attention to detail, like strategically placed tie down points and integrated splashguards, to help ensure your stuff arrives in good shape. The Interlock Seatpost Rack brings locking functionality to Blackburn's versatile seatpost mounted design, along with side rails that allow you to mount panniers.