A flooring material comprises sheet-shaped floor elements (1) with a mainly square or rectangular shape. Each of the floor elements (1) is provided with a male joining member (10 I ) on a first edge (2 I ) while a second edge (2 II ) of each of the floor elements (1) is provided with a female joining member (10 II ). The floor elements (1), on a third edge (2 III ), are provided with a male vertical assembly joining member (10 III ) while a fourth edge (2 IV ) is provided with a female vertical assembly joining member (10 IV ). The male and female vertical assembly joining members (10 III and 10 IV respectively) are provided with one or more hooks (23) with matching under cuts (24) which, by being provided with mainly horizontal locking surfaces, limit the vertical movement between two joined adjacent floor elements (1). The joint between two joined floor elements (1) further comprises cavities (6), and said hook (23) is constituted by a separate part (7) which is placed in a cavity (6). Two adjacent edges (2) of a floor element (1) at the same time, and in the same turning motion can be joined with a floor element (1) adjacent to the first edge (2 I ) and a floor element adjacent to the third or fourth edge (2 III and 2 IV respectively).