Water supply and sewer manholes are used to cover inspection wells of various purposes: sanitary-domestic, gas, water, heat supply, storm sewer, etc., to prevent foreign objects from entering the system, as well as to prevent accidents. The cover of a sewer manhole usually has a round shape so that it cannot fall into the manhole in any position. Depending on the material of manufacture and the application area, sewer manholes are divided into light (load class A15) - used in parks and pedestrian areas, medium (B125) - on sidewalks, parking lots, and driveways in urban parks, and heavy (C250) - on urban roads with high traffic intensity.