A building panel (1) has a major plane and is configured to interengage with at least one other adjacent like panel. The panel (1) has two major side surfaces (16) which are parallel to the major plane, and four major edge surfaces (2, 3) forming a perimeter (4) of the panel (1). An over-center camlock mechanism (7) is retractably extendable from each major edge surface (2, 3). Each major edge surface (2, 3) has a recess with an associated recess (17) at each major side surface (16), so that each recess is adjacent to at least one other recess. There is a pin in each recess and any over-center camlock mechanism (7) is latchingly engageable with the pin in any one of the recesses of the adjacent like panel so that the major planes of the two panels, when interengaged, are selectively parallel and coincident or perpendicular.