The extension of flaps (other than plain or split flaps), and including leading edge flaps will increase both the camber of the airfoil, and the wing area. Increases in both of these will increase CL. The path which air must follow over the top of the wing is lengthened with the increased camber resulting from flap extension. If CL at the approach to stall is being considered, the increased leading edge radius resulting from Kruger flap extension will delay the separation of airflow, similarly to extended slats, or fixed slot. Delaying the separation of airflow will delay the stall (and seem to increase CL), though this characteristic is only really important approaching stall.