Abstract: In a roughness scanner comprising a scanning arm with a scanning needle mounted at one end thereof, a skid carrier having an end supporting a skid with the scanning arm extending along the skid carrier in spaced relationship therefrom, the skid has at one side a guide late including an opening through which the scanning needle extends and a space formed above the guide plate which space is open at least at one side thereof down to the guide plate, so that any liquid collected by the needle and moving upward into the space above the guide late can flow again out of that space.