what is a door jamb

A door jamb, also known as a doorpost, is the vertical portion of the door frame onto which a door is secured. It is one of the posts which sit on either side of the door, forming the vertical portions of the door frame. 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 accuracy of the plumb (i.e. true vertical) and strength of the doorjambs vitally important to the overall operational durability and security of the door. The door frame is comprised of several parts, including the door jambs, sill, and head. The head jamb is the top horizontal section of the door or window frame.