A set comprising a first panel with a first main plane and a first panel surface, and a second panel with a second main plane and a second panel surface, and a mechanical locking device with a junction plane, wherein the mechanical locking device is configured for locking a first edge surface of the first panel to a second edge surface of the second panel at the junction plane, wherein the first main plain is perpendicular to the second main plane and the junction plane is extending at a first angle (α) to the first main plane, wherein the mechanical locking device comprises at least one rod-shaped element at the first edge surface and at least one insertion groove at the second edge surface, wherein the rod-shaped element is configured to be inserted into the insertion groove, wherein the rod-shaped element extends at a second angle (β) from the first edge surface, wherein the insertion groove extends into the second edge surface at a third angle (γ) from the second edge surface, wherein the mechanical locking device further comprises at least one locking groove at the first edge surface or at the second edge surface and at least one locking part at the other of said first or second edge surface, wherein the locking groove comprises at least one locking surface extending at a fourth angle (δ) from the first edge surface or from the second edge surface, the locking part is configured to be inserted into the locking groove and lock against the locking surface, and the second angle (β) is different than the fourth angle (δ), wherein the first angle (α) between the junction plane and the first main plane is 45°, and wherein the mechanical locking device is configured to obtain the locked position by displacing the first panel relative the second panel in an assembly direction, which is parallel with the first panel surface and parallel to a length direction and/or axial direction of the rod-shaped element, characterised in that the second angle (β) is within the range of 30° to 60°, or within the range of 40° to 50°, or 45°. wherein the mechanical locking device comprises at least one rod-shaped element at the first edge surface and at least one insertion groove at the second edge surface, wherein the rod-shaped element is configured to be inserted into the insertion groove, wherein the rod-shaped element extends at a second angle (β) from the first edge surface, wherein the insertion groove extends into the second edge surface at a third angle (γ) from the second edge surface, wherein the mechanical locking device further comprises at least one locking groove at the first edge surface or at the second edge surface and at least one locking part at the other of said first or second edge surface, wherein the locking groove comprises at least one locking surface extending at a fourth angle (δ) from the first edge surface or from the second edge surface, the locking part is configured to be inserted into the locking groove and lock against the locking surface, and the second angle (β) is different than the fourth angle (δ), wherein the first angle (α) between the junction plane and the first main plane is 45°, and wherein the mechanical locking device is configured to obtain the locked position by displacing the first panel relative the second panel in an assembly direction, which is parallel with the first panel surface and parallel to a length direction and/or axial direction of the rod-shaped element, characterised in that the second angle (β) is within the range of 30° to 60°, or within the range of 40° to 50°, or 45°.