Like a traffic controller for two guitars.
So you're out on a gig playing both acoustic and electric guitar, and want to use the same effects pedalboard, but don't want to keep plugging and unplugging your instruments. The solution simple, thanks to the Carl Martin Route Box footswitch. The double A/B footswitch pedal routes 2 guitars to either of two amps. Simply connect the 2 guitars to the Carl Martin Route Box's instrument inputs, and plug the route box output into your pedalboard. Connect the pedalboard into the Route Box input, and back out to your amp. You can even plug into an additional amplifier for even more control of each instrument's sound. The Carl Martin Route Box's amp select footswitch keeps the two instruments, two amps, and one pedalboard routed and dedicated.
A convenient way to route two guitars through the pedalboard to up to two amplifiers.