It’s Friday Riddle Time!

I have keys but no locks. I have a space but no room. You can enter but you can’t go outside. What am I?

This one tricks you by having you think about space that can be entered. Then it gets you to merge that with a space without rooms where you can’t leave. You might even be hung up on those keys. That’s where you should linger. Think about that word. What are some other meanings of “keys”—especially that don’t require locks? Comment below with your answer