There is disclosed an elongate structural element (10). The element (10) includes an inner plate (12) having first and second opposing planar surfaces (14, 16). The element (10) further includes first and second outer sections (18, 18′). Each of the outer sections (18, 18′) comprises a central wall (20) having a pair of longitudinal grooves (32, 34). Each of the outer sections (18, 18′) further comprises a pair of side walls (22, 24) extending from the central wall (20) to define a generally U-shaped channel (30). The longitudinal grooves (32, 34) depress into the U-shaped channel (30). Each of the outer sections (18, 18′) further comprises a pair of flanges (26, 28) respectively extending outwardly from the pair of side walls (22, 24). The flanges (26, 28) of the first outer section (18) are attached to the first planar surface (14) of the plate (12) and the flanges (26, 28) of the second outer section (18′) are attached to the second planar surface (16) of the plate (12) such that the U-shaped channels (30) are substantially closed by the inner plate (12) and opposed to each other.