Abstract: A structure for determining shelves and items of furniture, formed by nodes (1) and tubular profiles (2). Each node (1) has at least two arms (1.2) fitted and fastened inside the ends of each section of tubular profile (2), which is a single-body piece along the entire inside of an internal shape (2.1) with a square external edge. Each arm (1.2) of the node (1) has a part (1.2.1) corresponding to the internal square shape (2.1) with a square polygonal edge, the corners have bevels along the length with screw threads (1.2.2) extending parallel to the longitudinal axis of each arm, such that by inserting each arm (1.2) into a tubular profile (2) and rotating relative to one another, the crests of the screw threads (1.2.2) engage against the internal faces of walls (2.2) of the internal square shape (2.1), fastening each node (1) to a respective tubular profile (2).