To blindfold the interior of a housing body by effectively fixing the cover of integral molding to a service hole without fault by easy designing and low manufacturing cost by dispersing a plurality of locking pieces on the rear surface of a cover covering the front surface of the hole.

A cover 4 is mounted at the sidewall 2 of a housing body 1 via a hinge 5, the front surface of a service hole 3 is covered with the cover 4, and the interior of the body 1 is blindfolded. In the case that the components and the like in the body 1 are inspected, regulated and replaced, when the cover 4 is rotated counterclockwise (arrow) at the hinge 5 as a fulcrum, hooks (locking pieces) 41, 42 are removed from the hole 3, and the hole 3 is opened. After the inspection is executed, when the cover 4 is rotated clockwise, the hooks 41, 42 are engaged with the peripheral edge of the hole 3, the cover 4 is fixed to the sidewall 2, the front surface of the hole 3 is covered with the cover 4, and the interior of the body 1 is again blindfolded by resetting it to the original state.