A cajon drum is essentially a wooden box with snares inside designed to produce a multitude of percussion sounds. The large portion of the striking area makes a sound similar to a bass drum, while the top edge of the striking area utilizes the internal snares to make a higher-pitched sound similar to a snare drum. Tuning a cajon drum is a different process than tuning traditional drums, since it uses a set of screws instead of tuning lugs.
Strike the top of the striking area with your hand to trigger the snare sound and determine if it needs to be lower or higher. Turn the center top screw clockwise to raise the pitch or counterclockwise to lower the pitch.
Strike to the right or left of center to trigger the slap sound. Adjust the two screws to either side of the center screw to tune the slap sound up or down.
Strike the castanets on either side of the top portion, if your cajon includes castanets. Tighten the screw in the middle of each castanet to raise the pitch, or loosen it to lower the pitch.
Strike the center of the large portion of the striking area to trigger the bass sound. Tighten the remaining screws to raise the pitch of the bass sound, or loosen the remaining screws to lower the pitch of the bass sound.
Make small adjustments to the screws, then test the sound before making more adjustments. This will help you avoid tightening or loosening the screws too much.