A method, a locking device and a set of panels, including a panel and an adjacent panel, wherein the panel includes a groove and at least a first hole connected to the groove via an opening, the adjacent panel includes a first edge that is configured to be arranged in the groove of the panel and a second hole that is configured to be arranged at the opening when the first edge is arranged in the groove, and the panel includes a locking device configured to lock the first edge of the adjacent panel in the groove of the panel, wherein the locking device includes a locking pin and a flexible element, the flexible element is configured to move the locking pin from a locking position to a mounting position and to, when flexed back, move the locking pin from the mounting position to the locking position.