Abstract: Leaf (4) of a sliding window (1) or sliding door, whereby this leaf (4) has a horizontal profile (13) and an upright side profile (12) perpendicular to the horizontal profile (13), whereby the horizontal profile (13) is provided with a lock plate (10) for a lock (9), whereby the leaf (4) is equipped with an adjustment mechanism to be able to adjust the position of the lock plate (10) in the direction (P) in which the horizontal profile (13) extends and to be able to secure the lock plate (10) to the leaf (4), whereby the adjustment mechanism can be operated from the side where the side profile (12) is located.