In Australian commercial construction projects, a joist refers to a horizontal structural member that spans an open space and supports the floor or ceiling above. Joists are typically made of wood, steel, or concrete and are used to distribute the weight of the floor or ceiling and any loads applied to it, such as furniture, people, or equipment.

In the context of Australian commercial construction projects, a "joint" refers to a point where two or more components or materials are connected or come together. Joints are critical in construction as they ensure structural integrity, accommodate movement, and provide a seal against environmental elements.

In Australian commercial construction projects, a jamb refers to the lining or side-post that forms the sides of a door or window frame, fireplace, or other opening in a wall . It is a vertical element that makes up the frame of a door or window, and is typically made of wood, metal, or other materials.

In Australian commercial construction projects, a "jack rafter" refers to a type of rafter that is shorter than the full length of the roof slope. Jack rafters are used in roof framing and are typically found in hip and valley roof structures. They extend from a hip rafter to the eave or from a valley rafter to the ridge.