The manhole covers in London are usually made of metal or concrete , though plastic (composite) covers also exist.
London has a relatively large number of covers with transparent sections, which were typically placed above basements to allow sunlight to pass through into them .
The covers come in rectangular , square , circular , octagonal , or elliptical shapes.
London also has a relatively high number of covers with unique shapes: some resemble a bear’s head (especially when rotated 45 degrees counterclockwise) , others have a square or rectangular form ending in a trapezoid , triangular or nearly triangular , square with protruding edges , or hexagonal .
A small number of round covers intended for pavements are framed in a square border, making it easier to lay tiles around them .

The colored covers found in London are temporary ones used to cover ducts . No golden covers were found, except for a single cover with a golden label or information-related covers .
The city emblem does not appear on the covers.

Many covers belong to Thames Water, the water supplier for the London area , to the General Post Office (GPO) , the Metropolitan Water Board (MWB) , the communications company BT , or to TfL – Transport for London .

The function of the cover is not marked on many covers. When it does appear, it is often related to water (hydrant, water meter) , a communications provider’s name , or CATV (cable television) . Drainage covers can be identified by their characteristic drainage slots .

Coalholes
Coalholes are covers from the era when houses were heated with coal. Coal sacks were poured through these openings so coalmen didn’t have to enter the houses.
These covers were used in the 19th and early 20th centuries and can still be found throughout London.
A coalhole cover even serves as the logo of the website .

Walking Routes and Information
Some covers do not seal manholes (or other underground chambers) but serve as informational markers or route indicators — such as the Belsize Walk , the Princess Diana Memorial Walk , the Jubilee Walkway , and others.

Manufacturers
Many covers do not bear the manufacturer’s name. Interestingly, the most common manufacturer in London is the French company PAm .
Other common (mainly British) manufacturers include Peter Savage , Broads Manufacturing , Stanton , and Hayward Brothers , among others.

Standards
The most common standards are the European standard EN124 with various load classes (A15–F900) and the British Kitemark and BS497 standards.
Other, less common standards include BS5834 (British) , SGS (European) , EN1433 (European) , and others.