A system and method for retrieving information in a distributed table by partitioning a search key. One end of each insulator tube is fixed to the inside of the tank. Then bump-formation positions are inspected based on the second bump inspection images, and degrees of crush of bump vertex portions are inspected based on the respective first bump inspection images. An adjusting mechanism is provided for adjusting the plurality of slats and a drive shaft for rotatably driving the adjusting mechanism in opposite directions with the adjusting mechanism being adapted to rotatably engage the drive spool and wherein a lost-motion drive connection is operatively included between the adjusting mechanism and the drive spool.