When doing a quick sweep through a house looking for subjects, an interior door with a “privacy lock” can slow things down, giving the subject inside a chance to arm-up or head out. These locks are the type with a small round hole where the keyhole would be. Often knocking the door down is not practical, which makes an interior door key a good addition to your duty keychain. It’s not much more than a straight piece of wire with a loop to hold on to, but it can be a quick solution to this type of obstacle.