Abstract: A structural coupler for joining two storage racks of a mobile rack system. The coupler includes three separate components that are movable relative to each other to allow for relative movement between adjacent storage racks while providing the structural stability to prevent tipping of the storage racks. The coupler includes a coupling bracket that includes a pair of tabs that extend through open slots formed in a movement bracket and through receiving slots formed in a receiving bracket. A removable connector prevents separation of the coupler in the assembled condition while the size of the coupling tabs relative to the open slots allows the three components to move relative to each other. A series of individual couplers can be used along the height of the uprights that form part of each of the individual storage racks.