Building panel with a mechanical locking system

A set of panels, provided with a mechanical locking system comprising:

• a displaceable tongue, which is arranged in a displacement groove at a first edge of a first panel,
• a first tongue groove at a second edge of an adjacent second panel, the displaceable tongue being configured to cooperate with the first tongue groove for locking of the first and second edges in a vertical direction in a locked position,
• wherein the displacement groove comprises a first opening and the first tongue groove comprises a second opening,
• wherein at least a part of the displaceable tongue is configured to be pushed into the displacement groove during assembling of the first and second panels and spring back to a position in which an outer part of the displaceable tongue cooperates with the first tongue groove for the locking in the vertical direction in the locked position,
• wherein the first opening and the second opening are horizontally open and a vertical height of the first opening is greater than a vertical height of the second opening,
• wherein the panels are floorboards,
• wherein the outer part of the displaceable tongue is provided with a recess, and
• wherein an upper portion and a lower portion of the outer part of the displaceable tongue are in contact with the first tongue groove.