A rib post (10) has a hollow substantially triangular cross-section comprising composite material. The rib post (10) can form a structural member to join two adjacently placed components together, for example a spar and internal rib in a wing of an aircraft. The rib post (10) can be formed from first (12), second (14) and third (16) walls. The first wall (12) can abut a surface of one component and the second wall (14) can abut a surface of a second component. The first and second walls (12, 14) can be attached to the respective components, such as a rib and spar, to join them together. The third wall (16) joins together the first and second walls (12, 14) to form the hollow triangular section.