This description is about the importance of having a spare key to your home or other property. Having a spare key can be a lifesaver in situations where you have lost or misplaced your primary key. It can also be a great convenience if you need to give access to someone else, such as
From Wikipedia
Spare is a memoir by Prince Harry, Duke of Sussex, which was released in 2023. It was ghostwritten by J. R. Moehringer and published by Penguin Random House. An audiobook edition is narrated by Harry.