A place at the perimeter of a secured area where security personnel attempt to ensure that anyone or anything entering the area meets with its security policy. For example, in international airports around the world, the area where passengers board aircraft has a policy requiring no guns be carried except by authorized persons.

In the United States, these are popping up more and more in places like courthouses, concert halls and schools because a perceived increase in the threat of armed violence has led to more formal security policy being adopted in such places.