doorpost

Definition

The "doorpost" is a vertical beam on either side of a door, which supports the top of the door frame.

Just before God helped the Israelites escape from Egypt, he instructed them to kill a lamb and put its blood on their doorposts.
In the Old Testament, a slave could place his ear on the doorpost of his master's house and his master would hammer a nail through the slave's earlobe into the doorpost, as a sign of permanent ownership.