... , 2.the blowhole, 3.the tension bar, 4.inside jotting board, 5. The manhole cover, 6.inside ladder, 7.outside ladder, 8 ... .enters board, 9. The overflow outlet, 10.the water inlet, 11.the ... .The steel frame, 14. The drainage outlet.15. The drainage board, 16.The bottom board, 17.The outside jotting board, 18.the side ...