What is the purpose of different face masks on football helmets?

Each position has a different type of face mask to balance protection and visibility. Overall, most face masks are reinforced with an extra horizontal bar at the top of the face mask for better support and stability of the mask. Linemen usually have a closed-cage face mask that protects the nose and eyes with a vertical bar that runs up the middle of the face mask; a few horizontal bars also prevent injury to the face and eyes. The open-cage face masks have more visibility than closed cage, so there is no vertical bar that goes above the nose. These helmets have a few horizontal and vertical bars below the nose and are most used among skill-position players who need more visibility on the field. Skill-position face masks (used by quarterbacks and receivers) may also have masks that sit farther away from the players' faces and leave the chin exposed for easier mobility of their head. (This answer provided for NATA by the Saint Louis University Athletic Training Education Program.)