 If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an "overthrust" or "overthrust fault".Erosion can remove part of the overlying block, creating a "fenster" (or "window") – when the underlying block is exposed only in a relatively small area.When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called "klippen" (singular "klippe").