As a homeowner, you should reset the opener to prevent outsiders from opening the door with a remote that's set to a Liftmaster default code. A simple procedure allows you to reset the opener for one or more remotes.
doorsill - the sill of a door; a horizontal piece of wood or stone that forms the bottom of a doorway and offers support when passing through a doorway. doorstep, threshold. 1  doorway, room access, door, threshold - the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close; he stuck his head in the doorway.
What the heck is it? Anti-siphon/External Vacuum Breaker Devices. So as home inspectors one thing we are looking for are these mysterious little gadgets called a Vacuum Break or Anti-Siphon device on our exterior hose bibb/sillcocks. These external vacuum breakers are required at all hose bibbs/sillcocks. If they do not already have one built in you will need to add a screw on type of vacuum breaker. Hose bibb with integrated vacuum breaker. Hose bibb with concealed Vacuum Breaker. Another example of concealed vacuum breaker. Here are a couple of examples of screw on vacuum breakers. Typically these devices are designed with a spring loaded check valve that when the water is turned off the device vents to the atmosphere preventing backsiphonage.