A cover arrangement is provided for a launder channel of a clarifier tank. After selecting data from a set of data according to a desired condition inputted through a ten-key pad, a sequential index number is added to each piece of selected data. In the horizontal position, a free end of the magazine member is spaced apart from the end of the handle. A photoresist pattern is fox led by exposing each shot portion in the 1 to n regions using a split exposing condition in the 1 to n exposing ranges.