Refer to figure.
BAFFLES are fitted in the fuel tanks to help keep the fuel from sloshing around, dampening rapid fuel movement during aircraft manoeuvres (acceleration/deceleration/sideslip/etc). Large aircraft may be fitted with baffle check valves, which allow the fuel to flow inboard but not outboard towards the wingtips.

• Why are Baffles important?
  Consider a sudden pitch-up into a climb or a sudden acceleration: Now, the fuel will rush backwards, shifting the centre of gravity backwards. If this happens suddenly and the fuel starts oscillating, the aircraft will fly a wavy flight path without pilot input.