Jack rafter - A rafter that spans the distance from the wall plate to a hip, or from a valley to a ridge.

Jamb - The side and head lining of a doorway, window, or other opening.

Joint - The space between the adjacent surfaces of two members or components joined and held together by nails, glue, cement, mortar, or other means.

Joint Cement - A powder that is usually mixed with water and used for joint treatment in gypsum-wallboard finish. Often called "spackle."

Joist - One of a series of parallel beams, usually 2 inches in thickness, used to support floor and ceiling loads, and supported in turn by larger beams, girders, or bearing walls.