A doorjamb is the vertical portion of the frame onto which a door is secured. The jamb bears the weight of the door through its hinges, and most types of door latches and deadbolts extend into a recess in the doorjamb when engaged, making the "true" (leveling) and strength of the doorjambs vitally important to the overall operational durability and security of the door.
The word "jamb" comes from the French "jambe", meaning "leg".[1]