The bearings we have defined so far are the basic types, which constant feature is the fact that they allow all-ways movements and rotation. However, movements can be limited in one or all ways, thus obtaining guided or fixed bearings, respectively. In the first case -guided bearings- the restriction is obtained by means of guides parallel to the supporting axe that allows movement. To make friction as low as possible, PTFE and stainless steel sheets are welded to the guides.