Police in some parts of England and Wales are trying out a scheme to get kids to report anyone they know is carrying a knife by text.
Young people can send an anonymous message to a special Crimestoppers number, so no-one will know that they've sent it.
The messages will then be passed over to police officers.
Richard Spedding from Lancashire police said he hopes the scheme will get more kids to help stop knife crime.
The ten areas taking part in the scheme are London, Essex, Lancashire, West Yorkshire, Merseyside, the West Midlands, Greater Manchester, Nottinghamshire, South Wales, and Thames Valley.
If you live in one of those areas and are worried that someone is carrying a knife, text their name or nickname, school, year, and area or postcode to 88551.
But don't forget to delete the message from your phone's sent box if you want to be really sure that no-one else will know you've sent it.
The number should only be used for information about knife crime, and people who want to report other things should call the usual Crimestoppers number 0800 555 111.
If you're worried about knife crime and don't live in an area covered by the scheme, you can get advice from the charity's special website, called Shadow CS, for kids via the link on the side of the page.