Idioms: Safety

There are idiomatic expressions in English that can be used to talk about safe situations or actions.

Some of them include the words SAFE and SAFETY.

If you are in safe hands, you are sure that you are with somebody who will take good care of you.
Example: You can leave your child with us.  He'll be in safe hands here.

If you do something to be on the safe side, you take some precautions, or you do something in order to avoid any risk or danger.
Example: I'll check that she's sent the document.  I just need to be on the safe side.

A safety valve is a way of expressing your negative feelings openly or releasing your negative feelings, but without harming other people.
Example: He uses his boxing classes as a safety valve for all the frustration he feels.

A safety net is something  that provides security in case of misfortune or difficulty.
Example: The unemployment fund program provides a safety net for people who have lost their jobs.

When you want to tell people that if they act together they may have less chances of something bad happening to any of them (instead of doing things individually), you say that they should something together as there's safety in numbers.
Example: I think we should all go and complain about this situation together.  You know, there's safety in numbers, they can't fire us all.