In the PSNI there are also Special constables known as a Reserve Constable which can be part or full time positions.

The ranks and their insignia correspond to those of other UK police services, with a few modifications.
Sergeants' chevrons are worn point-up as is done in the United States, rather than point-down as is done in other police and military services of the United Kingdom.
Sergeants do not wear numbers as their counterparts do in other UK police services.
The six-pointed star & saltire device from the PSNI badge is used in place of the Crown in the insignia of superintendents, chief superintendents and the chief constable.
The rank insignia of the chief constable, unlike those in other parts of the UK, are similar to those of the Commissioner of Police of the Metropolis and the Commissioner of the City of London Police.
In the PSNI there are also Special constables known as a Reserve Constable which can be part or full time positions.
The ranks and their insignia correspond to those of other UK police services, with a few modifications. Sergeants' chevrons are worn point-up as is done in the United States, rather than point-down as is done in other police and military services of the United Kingdom. Sergeants do not wear numbers as their counterparts do in other UK police services. The six-pointed star & saltire device from the PSNI badge is used in place of the Crown in the insignia of superintendents, chief superintendents and the chief constable. The rank insignia of the chief constable, unlike those in other parts of the UK, are similar to those of the Commissioner of Police of the Metropolis and the Commissioner of the City of London Police.
Police Service of Northern Ireland