A coal hole is a hatch in the pavement (sidewalk, in US usage) above an underground coal bunker. They are sometimes found outside houses that existed during the period when coal was widely used for domestic heating from the early 19th century to the middle 20th century. In Britain they became largely obsolete within the major cities of the UK when the Clean Air Act forced a move towards oil and gas for home heating.
The coal hole allowed the easy delivery of coal, generally in sacks and often from horse-drawn carts, to the house's coal bunker. The location of the coal hole on the street minimised the distance the sacks needed to be carried and meant that dusty sacks and delivery men did not need to enter the house.
The hatch is typically about 12 to 14 inches (30 to 35 cm) in diameter and consists of a cast iron ring set into the pavement, with a circular cover, often made of cast iron alone but sometimes containing concrete or glass panes or small ventilation holes. There are three main reasons for the circular shape of the coal hole plate: a circular disc can not accidentally fall through its own hole (unlike a square or rectangular one); its weight means that it can be rolled rather than carried or lifted; and the absence of corners allows for a reduced risk of damage to it. Hatches have an internal latch that prevents the cover being lifted from the outside. On some streets there are a variety of types of cover reflecting the fact that the coal holes were installed at different times by different builders after the houses were built.