Its main purpose is to enable precise and repeatable milling of grooves, especially for making wooden joints. The fence acts as a guide that rests on the edge or surface of the material to be machined and stabilizes the milling machine in the desired position. It makes it easy to create grooves for joints, such as joints for flat pins, known as "slats", or for other inserts. It ensures that the groove is milled at the correct distance from the edge and at a precise angle, which is key to creating a strong and precise-fitting joint between two pieces of material.