Cleaning liquid is easily prevented from adhering to a main wiping side of a windshield glass when a main wiping side wiper, that rotates reciprocally, moves to a reciprocal rotation inbound side. In one aspect, manufacturing and assembly of the fixture uses clean-room light techniques. In another embodiment of the invention, edge segments are assigned a priority such that the correction of a lower priority edge does not hinder a desired OPC correction of a higher priority edge. Each user may incorporate modifications into their copy, which will later be shared by the rest after a synchronization stage. The measured elevations allow formation of a topological map depicting sub-micron structural features of the surface.