A refining surface (2) of a refiner stator (4) for a refiner for defibrating lignocellulose-containing material has a feed edge (17) oriented in the direction of the feed flow of the material to be refined, and a discharge edge (16) oriented in the direction of the discharge flow of the material refined. The surface (2) has blade bars (10) with grooves (11) therebetween, and at least one dam (12) in a groove (11). The dam has an upwardly rising guiding surface (13) from the blade groove bottom (15) for guiding the material to be refined and the material already refined out of the blade groove. The upward direction of the guiding surface (13) is from the direction of the discharge edge (16) of the refining surface (2) in the direction of the feed edge (17) of the refining surface (2).