A panel has a core of wood material or a wood material/plastic mixture, a top and an underside, and two opposite side edges, which have profiles that correspond to each other such that two identically configured panels can be connected and locked to one another in the horizontal (H) and vertical (V) directions by an essentially vertical joining movement. The locking in the horizontal direction (H) can be brought about by a hook connection with an upper locking section having a hook element and a lower locking section having a hook element. The locking in the vertical direction (V) can be brought about by at least one tongue element that is formed from the core in one piece and can be moved in the horizontal direction (H). The at least one tongue element provided on the lower locking section is free with respect to the core in the direction of the opposite side edge by means of an essentially vertical slot and during the joining movement snaps in behind a locking edge extending essentially in the horizontal direction (H), which locking edge is embodied on a locking projection. The tongue element is connected to the core on at least one of its two ends in the direction of its side edge (II), and the width (B1, B2) of the locking edge is different in size over the length (L) of the opposite side edge (I).