Utility and control-cabinet key heads come in a variety of different shapes and sizes known as ‘profiles.’
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
The square pin is a very common shape of valve head…
…and the square socket is a common lock profile.
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 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.
Each manufacturer chooses different sizes for their key but the sizes usually cover 5mm to 8mm pin or socket heads.
Triangle
The triangular prism-shaped pin is another common type of lock shape. Locks or valves with triangle sockets are also relatively common.
Utility and control-cabinet keys often have at least one triangle socket and occasionally a stepped triangle pin head.
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.
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
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.
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
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.
Other utility and control-cabinet keys have bit sockets in the body of the key. The sockets are sometimes referred to as ‘bit adaptors.’
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 profiles sometimes occur on utility and control-cabinet keys. Half-moon pin profiles are not available on these tools.
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.
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
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.
