Manhole covers prevent anyone or anything from falling into a manhole and keep out unauthorized persons.
They enable the manhole to be accessed safely when required for maintenane or repair work.
Generally made from cast iron, concrete or a combination of the two - this makes them inexpensive, strong, and heavy, usually weighing more than 50 kilograms (110 lb). The weight helps to keep them in place when traffic passes over them, and makes it difficult for unauthorised people without suitable tools to remove them.
Manhole covers have various weight classes depending on their application. For example, a Class A15 (cast iron) manhole cover can withstand a maximum weight of 1.5 tonnes. It would typically be restricted to light duty applications, such as in pedestrian areas, gardens, patios and driveways; whereas a F900 class manhole cover would typically be used in docks, airports and other extreme heavy-duty application