| 摘要 |
PROBLEM TO BE SOLVED: To provide a bilge pit drillhole centering instrument allowing anyone to easily and accurately perform the operation of marking a centering position on the outer peripheral surface of a bilge pit with a marker without requiring particular techniques and to provide a through-hole in an accurate position to achieve uniform adhesiveness at the surface of contact between an extension pipe of a water pipe and rubber packing fitted into the through-hole, thus enhancing watertightness. SOLUTION: The centering instrument for a through-hole drilled in a bilge pit is used when a water pipe such as a waste water inflow main pipe or a waste water outflow main pipe is connected to the bilge pit. The instrument comprises a mounting part for mounting the end portion of the water pipe thereto, and a marker part for marking a centering position on the outer peripheral surface of the bilge pit. The axis of the mounting part is the same as the axis of the marker provided at the marker part.
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