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What are the different types of utility and control-cabinet key heads?

Shop for Utility and Control Cabinet Keys

Profiles of a utility and control or service cabinet key Utility and control-cabinet key heads come in a variety of different shapes and sizes known as ‘profiles.’
One size of pin key of a utility and control or service cabinet can fit multiple sizes of socket locks. Note on sizes: the measurements in the product description are the sizes of lock that the key will fit NOT the size of the key itself. Some profiles are designed to fit more than one size of lock so the measurement indicated might be a range (e.g. 9-10mm) rather than a single number. All measurements, except the ¼ inch bit and socket, are in millimetres.

Square

Square pin head of a radiator valve The square pin is a very common shape of valve head…
Public bin with a square socket lock that can be opened by a square pin headed utility and service or control cabinet key. …and the square socket is a common lock profile.
Two sizes of square socket profiles of a utility and control or service cabinet key Utility and control-cabinet keys usually have two or more square socket profiles. Some will also have a range of pin profiles on a stepped pin head.
The size in millimetres of a square socket is the measurement of the length of one side of the square. The measurement in millimetres in the product description is the length of the sides of the square-shaped part of the lock or valve head that the utility and control-cabinet key will fit.
Stepped pin head of utility and service or control key showing multiple sizes Each manufacturer chooses different sizes for their key but the sizes usually cover 5mm to 8mm pin or socket heads.

Triangle

Triangle pin head of a meter cupboard lock to be opened by a utility and service or control cabinet key. The triangular prism-shaped pin is another common type of lock shape. Locks or valves with triangle sockets are also relatively common.
Utility and service or control cabinet key in a lock, with a triangle socket profile visible Utility and control-cabinet keys often have at least one triangle socket and occasionally a stepped triangle pin head.
A triangle profile of a utility and control or service cabinet key has cut-off corners. When the triangle profile is drawn in a diagram, it is represented by a normal triangle with pointed corners but most utility and control-cabinet keys, locks and valves actually have triangles with cut off corners.
Measurement in millimetres of triagnle sockets and pins that utility and service or control cabinet keys can open. The measurement in millimetres in the product description indicates the length from top to bottom of the triangle shape. Triangle lock or valve sizes that utility and control-cabinet keys can turn tend to vary between 8mm and 11mm.

Circle-with-fins

circle-with-fins lock and utility and service or control-cabinet key profile The ‘circle-with-fins’ profile, also known as a ‘two-way key’ profile, is one size and is commonly used to unlock control or service cabinets. Bizarrely, it is not always in the product description so check the tool, its picture or your supplier before purchasing.
Circle-with-fins key profile of a utility and service or control-cabinet key fits locks that have a 3-5 millimetre pin If a measurement is present it will be indicating the internal diameter of the circle shape of the lock (unless otherwise stated) in millimetres. Circle-with-fins profiles fit locks that are 3mm (⅛”) to 5mm (13⁄64″), inclusive.

Bit socket

1/4" bit socket within a triangle or square socket of a utility and service or control-cabinet key Many utility and control-cabinet keys are sold with a ¼” reversible screwdriver bit (see What utility and control-cabinet accessories are available?) and will have a socket or slot it can fit into to create a small screwdriver. Often the bit socket is within another socket profile, usually a triangle socket or square socket.
Bit socket in main body of utility and control or service cabinet key Other utility and control-cabinet keys have bit sockets in the body of the key. The sockets are sometimes referred to as ‘bit adaptors.’
There is sometimes a magnet at the base of the bit profile in the utility and service or control cabinet key Some bit sockets have a small magnet in the base of the socket to hold the bit in place while performing a task.

Half-Moon

Half moon socket profile on a utility and service or control cabinet key Half-moon socket profiles sometimes occur on utility and control-cabinet keys. Half-moon pin profiles are not available on these tools.
A circle key in comparison to a half-moon key of a utility and service or control cabinet key to explain how the key works. The flat side of the profile provides a surface for the wrench to push against to turn the valve or lock. If it was a circle, the key would just slip round and the lock would stay still.
Half moon keys of utility and control or service keys are not good for valves or locks in hard to reach places. They are not as easy to use as square locks because the socket of the key can only be placed over the head of the lock one way. If the valve is in a hard-to-reach place, the wrench might not be able to turn.

Cross

The rare cross socket profile of a utility and control or service cabinet key is measured from top to bottom. Cross socket profiles are rare but do feature on some utility and control-cabinet keys. The measurement in millimetres is from top to bottom of the cross.