A coal hole is a hatch

Hatch

Hatch may refer to:* Hatching, also called "cross-hatching", an artistic technique used to create tonal or shading effects using closely spaced parallel lines* Hatching, the emergence of a young animal from an egg...

 in the pavement

Sidewalk

A sidewalk, or pavement, footpath, footway, and sometimes platform, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade and is normally separated from the vehicular section by a curb...

 (sidewalk, in US usage) above an underground coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 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 redundant within the major cities of the UK when the Clean Air Act

Clean Air Act

A Clean Air Act is one of a number of pieces of legislation relating to the reduction of airborne contaminants, smog and air pollution in general. The use by governments to enforce clean air standards has contributed to an improvement in human health and longer life spans...

 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 cart

Cart

A cart is a vehicle designed for transport, using two wheels and normally pulled by one or a pair of draught animals. A handcart is pulled or pushed by one or more people...

s, 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

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 ring set into the pavement, with a circular cover, often made of cast iron alone but sometimes containing concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 or glass

Glass

Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

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.