A set comprising a first panel, a second panel (20, 20a) and a mechanical locking device for locking the first panel to the second panel (20, 20a), wherein - the first panel comprises a first edge surface and a first panel surface, - the second panel (20, 20a) comprises a second panel surface and a second edge surface, - the first edge surface is facing the second panel surface in a locked position of the first and the second panel (10, 20, 20a), - the mechanical locking device comprises a panel groove (133, 33) at a surface (21, 22) of the second panel (20, 20a), a flexible tongue positioned in the panel groove (133, 33), a rod-shaped element at the first edge surface and an insertion groove at the second panel surface extending from the second panel surface to the panel groove (133, 33), - the rod-shaped element having a longitudinal shape with a length direction which is parallel to the first panel surface and perpendicular to the first edge surface and comprises a first part at a first end, a second part at a second end and a recess in the second part, wherein the first part of the rod-shaped element is configured to be inserted into an attachment groove in the first edge surface and the second part of the rod-shaped element is configured to be inserted into the insertion groove, - the flexible tongue is configured to cooperate with the recess for a locking of the first panel to the second panel (20, 20a) in a first direction which is perpendicular to the second panel surface, - the rod shaped element further comprise a third part located between the first and second part (51, 52), having an extension perpendicular to the length direction that is larger than the extension of the attachment groove in the first edge surface in the corresponding direction, such that the third part is configured to limit the depth that the first part could be inserted into the attachment groove, and - the attachment groove is a bottom-ended groove, such as a bottom ended drill hole, comprising a bottom surface which is positioned at a distance from the first edge surface that is larger than a length of the first part in the length direction. - the first panel comprises a first edge surface and a first panel surface, - the second panel (20, 20a) comprises a second panel surface and a second edge surface, - the first edge surface is facing the second panel surface in a locked position of the first and the second panel (10, 20, 20a), - the mechanical locking device comprises a panel groove (133, 33) at a surface (21, 22) of the second panel (20, 20a), a flexible tongue positioned in the panel groove (133, 33), a rod-shaped element at the first edge surface and an insertion groove at the second panel surface extending from the second panel surface to the panel groove (133, 33), - the rod-shaped element having a longitudinal shape with a length direction which is parallel to the first panel surface and perpendicular to the first edge surface and comprises a first part at a first end, a second part at a second end and a recess in the second part, wherein the first part of the rod-shaped element is configured to be inserted into an attachment groove in the first edge surface and the second part of the rod-shaped element is configured to be inserted into the insertion groove, - the flexible tongue is configured to cooperate with the recess for a locking of the first panel to the second panel (20, 20a) in a first direction which is perpendicular to the second panel surface, - the rod shaped element further comprise a third part located between the first and second part (51, 52), having an extension perpendicular to the length direction that is larger than the extension of the attachment groove in the first edge surface in the corresponding direction, such that the third part is configured to limit the depth that the first part could be inserted into the attachment groove, and - the attachment groove is a bottom-ended groove, such as a bottom ended drill hole, comprising a bottom surface which is positioned at a distance from the first edge surface that is larger than a length of the first part in the length direction.