Abstract: The disclosure relates to a hollow section elongated structural member comprising three parallel spaced channel section elements (13) with three panels (11) extending between the respective pairs of elements to form a hollow section member. The edges of the panels have edge formations (17) which are received in the channels, each edge formation being shaped to conform to a side wall (15) and adjacent base part (14) of a channel. Clamping members (18) are provided for each channel having a clamping face including a main part (19) flanked by said faces (21) to act in co-operation with the base and side wall of the channel (13) to clamp the respective edge formations of a pair of panels therein and screws (23) are provided for securing the clamping members to the channel to lock the edge parts of the channels in the channels and thereby create a rigid structue between the channels and panels.