I did this the other weekend.except replace "monsters" with "zombies." Someone was shooting off and I thought, "What if those are rifles? What if it's zombies?" This is why I choose not to watch scary movies! :) I've got "scary" covered.
Welcome Girl Scouts, go away Door to Door Salesman! "Unless your selling Thin Mints, NO SOLICITING". This would be great for thehome front door on a small sign above the doorbell or on the glass door of a business.