A knife amnesty is something the police use to try to get people to give up any illegal knives they may have.
During an amnesty people can hand in their knives at police stations without getting into trouble.
In some areas, secure bins are also put in places like schools, youth clubs and churches to encourage more people to dump their blades.
In the past, knife amnesties have been very successful, with people giving up thousands of illegal knives and weapons.
When an amnesty ends, tough punishments are reintroduced for anyone who's caught carrying a knife.
That can mean getting a huge fine or even being sent to prison.