Detailed instructions are issued by the military authorities which prescribe the components of the various types of military dress and the circumstances in which they may be worn.
In the interests of neat appearance, hygiene and certain operational requirements in regard to the use of equipment such as respirators, minimum standards are laid down for all ranks in relation to hairstyles, moustaches and beards.
A major review of these instructions was undertaken in 1986 and there are arrangements for their periodic re-assessment to ensure that they continue to meet modern service requirements.