When talking about a nostril strap we must say that it is a piece of BDSM equipment used in order to humiliate and punish the slave (submissive).
Also known as nose hook, as a part is attached to the nostrils and the other end to the head, with a strap.
A nostril strap is used to get the slave to bend the head backwards and it is an uncomfortable position for the slave and can be considered as a punisment instrument. It has to be used safely.