Building panel with a mechanical locking system

A set of panels is provided with a mechanical locking system comprising a displaceable tongue, which displaceable tongue is arranged in a displacement groove at a first edge of a first of the panels, the displaceable tongue is configured to cooperate with a first tongue groove at a second edge of an adjacent second of the panels, for locking of the first edge and the second edge in a vertical direction,

• wherein the displaceable tongue is of a longitudinal shape and resilient, a spring constant of the displaceable tongue varies in the longitudinal direction of the displaceable tongue, and a middle section in the longitudinal direction of the displaceable tongue has a higher spring constant than a first edge section of the displaceable tongue, and
• wherein the mechanical locking system is configured such that, during assembly of the first of the panels and the adjacent second of the panels, the first edge section of the displaceable tongue cooperates with a guiding surface of the second edge of the adjacent second of the panels before other sections of the displaceable tongue cooperate with the guiding surface,
• wherein an inner long edge of the displaceable tongue comprises protrusions arranged in the displacement groove, wherein the protrusions are adjacent to one another along the longitudinal direction of the displaceable tongue having the longitudinal shape, the protrusions are spaced along the longitudinal direction of the tongue, and the protrusions are bendable.