At high speeds, dynamic action of the lubricant film generates a hydro-dynamic force which lifts the saddle off the guideway. For good hydro-dynamic action, the sliding bodies should be inclined towards each other. They should form a liquid wedge. Most of the hydro-dynamic guideways have wedge-like inclined passages, on both sides of the lubrication grooves [Fig. 5.43]. Nearly 20% of the guideway width is left straight, since even hydro-dynamic guideways operate under semi-liquid friction, at the beginning of the machine operation and during braking.