I'm always armed & will never open a door to any one I don't know. I always let them know some one is home by asking "who is it" then telling them something like I'm not interested or to leave.
Never ignore a knock at the door because that says no one is home.
"Blessed be the Lord my strength,which teacheth my hands to war and my fingers to fight".
Psalm 144:1 KJV Be safe: Paul