A collapsible, elongate support structure module, wherein the module is configured to form a beam or part of a modular beam structure, the module having an uppermost side element comprising a first element part and a second element part ( 103") which between extreme ends of said uppermost side element are hinge connected to each other via a hinge connection, the two element parts ( 103', 103") being located in a common plane when the module is completely unfolded and stretched-out, wherein the module has: - a) first and second upright, rigid module end elements ( 101; 102), and - b) in addition to said uppermost located side element at least two further side elements ( 104; 105), and - wherein said uppermost side element and said at least two further side elements ( 104; 105) extend between said module end elements ( 101; 102) and form mutual angle with each other, each module side element ( 103; 104; 105) in longitudinal direction having a first extreme end and second extreme end which are hinge connected to said first and second module end elements ( 101; 102), respectively, and each of said at least two further side elements (104; 105) being constituted by a first element part ( 104'; 105') and a second element part ( 104"; 105") which between said extreme ends are hinge connected to each other via a respective hinge connection ( 113; 114) to enable rotation of said first and second element parts ( 103'; 103") toward or away from one another, the two element parts ( 104', 104"; 105', 105") of each of these further side elements (104; 105) being located in a common plane when the module is completely unfolded and stretched-out, characterized in - that any adjacent side elements ( 103, 104; 103, 105; 104, 105) of other two side elements ( 103; 104; 105) abut each other and make co-operating engagement ( 115', 115", 116; 104, 117; 105, 117) along one or a plurality of locations thereof, and - that a releasable locking device ( 115, 116) is provided at said one location or at least at one of said plurality of locations to interlock adjacent edges of said at least two adjacent side elements ( 103, 104; 103, 105; 104, 105) of said side elements ( 103; 104; 105). - a) first and second upright, rigid module end elements ( 101; 102), and - b) in addition to said uppermost located side element at least two further side elements ( 104; 105), and - wherein said uppermost side element and said at least two further side elements ( 104; 105) extend between said module end elements ( 101; 102) and form mutual angle with each other, each module side element ( 103; 104; 105) in longitudinal direction having a first extreme end and second extreme end which are hinge connected to said first and second module end elements ( 101; 102), respectively, and each of said at least two further side elements (104; 105) being constituted by a first element part ( 104'; 105') and a second element part ( 104"; 105") which between said extreme ends are hinge connected to each other via a respective hinge connection ( 113; 114) to enable rotation of said first and second element parts ( 103'; 103") toward or away from one another, the two element parts ( 104', 104"; 105', 105") of each of these further side elements (104; 105) being located in a common plane when the module is completely unfolded and stretched-out, characterized in - that any adjacent side elements ( 103, 104; 103, 105; 104, 105) of other two side elements ( 103; 104; 105) abut each other and make co-operating engagement ( 115', 115", 116; 104, 117; 105, 117) along one or a plurality of locations thereof, and - that a releasable locking device ( 115, 116) is provided at said one location or at least at one of said plurality of locations to interlock adjacent edges of said at least two adjacent side elements ( 103, 104; 103, 105; 104, 105) of said side elements ( 103; 104; 105).