The RepRap stepper driver (http://reprap.org/bin/view/Main/Stepper_Motor_Driver_2_3) runs fine with most steppers. But if you run it at its highest current (near to the maximum of 2A) the driver chip will get pretty hot.
The fan mount will allow you to attach an ordinary 12v CPU fan (34mm hole centres) to the stepper driver board to cool the driver chip. If you want you can use heatsink compound to stick a small SMT-type heatsink to the top of the chip to improve cooling even further.
Print the fan mount upside down in your 3D printer.
Attach all the wiring to the stepper driver PCB first.
Attach the fan to the mount, then attach that assembly to the PCB.
Solder the fan leads in parallel with the 12v supply to the board, taking care to get the polarity right (usually red = +; black = -).
The mount has been designed so that you can adjust the stepper-current-controlling potentiometer with a small screwdriver between the fan's blades. Turn it off first...