Manholes are installed for the maintenance and installation of urban underground infrastructure such as power supply, water supply, drainage, and sewage. They are generally located at the intersections, bends, diameter changes, or gradient changes of pipes. Depending on the number and angle of the nozzles, there are starting manholes, straight-through manholes, 45-degree elbow manholes, three-way manholes, and four-way manholes.

The manhole is composed of the manhole base, vertical shaft, cover, and related accessories. The manhole base is often made by a single injection molding process, utilizing fittings such as reducing joints, angle elbows, and rubber sealing rings to achieve variable pipe diameters and angles.