Flaps alter the wing's camber and angle of attack, both of which change the lift coefficient which changes flying speed - A glider's trimmed flying speed depends only on its lift coefficient and wing loading.

When used as ailerons, the inboard location of flaps limits their effectiveness in generating a roll-axis moment for a given amount of drag created, compared to ailerons. Therefore, when flaps function as ailerons, they generally aren't deflected as much as the ailerons (50% of aileron throw is common).

Full-span camber control (ailerons also functioning as flaps) is preferable, in order to avoid an abrupt change of camber and AOA at the flap/aileron junction.