igus® has three production processes for gear racks:
Rack and pinion gear is used where you are looking to convert the rotational movement of the pinion gear into a linear motion.
A rack is usually a square or round section of material which has straight teeth cut into it. The pinion gear is cylindrical gear who's teeth match with racking which enable them to mesh together. When they are working together they are known as a "rack and pinion system".
When designing a rack and pinion gear you need to ensure the they have matching modules. The module of the rack and the pinion gear dictates the size of the teeth, so to enable the rack and pinion gear to mesh together the size of the teeth must match.