When you go to the airport to get on a plane, you have to go through security checks. Since September 11, 2001, these checks have become far more strict.

Your luggage that goes in the cargo hold will be x-rayed. Your hand luggage will also be screened to see you aren't carrying any weapons.

Some people will have their luggage examined by hand to see exactly what they are carrying.

You also walk through a doorway that lets off an alarm if you have any metal in your clothing.