Abstract: A bi-stable hinge unit (10) of elastic material connects two inflexible end portions (12, 13) to take up two stable positions on either side of an intermediate unstable position. The hinge unit (10) comprises two equal elements (14, 15), each of which having two cantilever arms (18, 20), linked to each other by two folding lines (22) acting as a "living" hinge. A triangular rigid plate (16) is arranged between and defined by said folding lines (22). The elements (14, 15) are arranged substantially parallel to each other with a distance therebetween and forming the main hinge line between said end portions (12, 13). By swinging the end portions (12, 13) toward each other along the main hinge line, the four cantilever arms (18, 20) will start to deflect and act as springs and the two triangular plates (16) will rotate through approximately 180.degree. in a plane normal to the elements (14, 15).