Disclosed is a device for connecting and locking building boards comprising a top face (10) and a bottom face (11), especially floor panels (1, 2) that are provided with a core made of a wood material as well as a groove (3, 4; 5, 6; 18, 19) on two opposite lateral edges (I, II). Said building boards further comprise an insert (7; 8; 9) that is used for locking and can be inserted into the groove (3 or 4; 5, 6; 18, or 19) of one of the lateral edges (I, II). The boards (1, 2) are connected by displacing the boards in an essentially horizontal direction (Q) towards each other. The inventive device is characterized in that the insert (7; 8; 9; 17) is provided with at least one springy lip (7a, 8a; 9a; 17a) which extends towards the top face (10) or the bottom face (11).