You can often reverse your servo throw direction by turning it around or reversing the servo linkage. Sometimes there just isn't room under a turnout to do this. You can't reverse the servo direction by swapping wires since servos work by varying the pulse width and reversing the wires will just disconnect off the servo. In cases where you want to reverse the servo rotation direction, this servo reverser comes in handy. If you put this in line with the servo it will swap the two ends about the center. [It works by mirroring the pulse around 1.5 ms which is the center on a servo. I.e. if a 2 ms pulse is input, the reverser will output 1 ms and if a 1 ms pulse is input it will output a 2ms pulse.]