Cargo Buckle 7 E-Track Adapter Strap This Cargo Buckle 7 E-Track Adapter Strap will secure your cargo to your trailer in a quick and hassle-free motion. Its self-retracting, quick-release designs makes loading and unloading simple and easy. Dual-safety locks ensure that each ratchet arm stays in open or closed position while the self-retracting straps automatically wind up in the built-in housings and maintain constant tension on the straps for minimal ratcheting when tightening the straps down.