PURPOSE: To produce a body block which does not require to draw ruled lines, by staming in advance marks indicating an angle in the circumferential direction at the outer peripheral face of the opening of the body block for manhole and indicating the length from the opening, when manufacturing the body block.

CONSTITUTION: An inflow opening 4b and an outflow opening 4a are provided in a body block 4. In this time, angular graduations 4c beginning with 0deg., regarding the center of a foot rest 10 at the outer peripheral edge of the opening of the block 4 as the base of graduation are formed like a relief. The body block is turned until the center point of the outflow opening 4a and the inflow opening 4b coincides with the center point of a drilling machine to accurately bore the outflow opening 4a and the inflow opening 4b against the center point of the foot rest 10. In this way, the block can be simply bored in accurate positions.