We make two Cable Doublers. The first allows you to control two brakes with just one lever. The second allows you to control one brake with two levers. Why? Well, there are myriad applications: cyclocross, fixies, tandems, bike polo, tricycles, recumbents, cycles for those with special needs, those four-person bikes you see on beach boulevards, and so on. You could even link them both together for ultimate redundancy!