The kangha is a small wooden comb, worn in the hair under the turban and used twice a day.
Of the five kakars it is the one about ordinary maintenance. Long hair uncared for is matted hair, which was the mark of the ascetic orders the Sikh tradition explicitly separated itself from. The comb is the difference between uncut hair and renunciation.
That distinction is the whole argument between Guru Nanak Dev Ji and the jogis, and it is carried by a piece of wood four centimetres long.
They are traditionally made of wood, often boxwood or sheesham, by specialist makers, and they are among the few Sikh articles still made by hand in small workshops in Punjab.
It is the least discussed of the five and the one that says most about the tradition's attitude to the body.
The comb is used morning and evening and the hair is retied. The discipline is daily and small, which is the point of it.
The jogis whom Guru Nanak Dev Ji argued with wore matted hair as a mark of renunciation. Keeping the hair and keeping it clean rejects that, and rejects the idea that holiness requires leaving the world.
Wooden combs are still made by hand in a few places and the moulded ones sold everywhere now are the same shape. The shape has not changed.