 When the top of the excavation is the ground surface, it is referred to as a shaft; when the top of the excavation is underground, it is called a winze or a sub-shaft.Small shafts may be excavated upwards from within an existing mine as long as there is access at the bottom, in which case they are called Raises.A shaft may be either vertical or inclined (between 45 and 90 degrees to the horizontal), although most modern mine shafts are vertical.