Arrow Aimers, also known as Arrow Orbs, are objects that appear in Phantom Hourglass and Spirit Tracks. They are orbs that float in the air that have an arrow design, which points in a particular direction. If Link shoots an Arrow at the Arrow Aimer, the arrow will re-direct after hitting the orb and shoot out in the direction that the Arrow Aimer is pointing.
Link can change the direction that the Arrow Aimer is pointing by hitting it with his Sword, or other items in his inventory including the Boomerang or the Whip. Each time Link hits the Arrow Aimer, it will rotate clockwise.
Arrows Aimers first appear in Phantom Hourglass within the Temple of Courage, the same dungeon where Link first acquires the Bow. Link will often have to shoot arrows at the Arrow Aimer, which causes the arrows to deflect and hit distant switches, which allow Link to navigate further areas of the dungeon.
In Spirit Tracks, Arrows Aimer take on an identical appearance as they do in Phantom Hourglass, but there are now more elaborate puzzles involving these orbs. Link or a Possessed Phantom can lift up the orbs and toss them around. A Possessed Phantom can even hoist the orb over his head. In parts of the Tower of Spirits, this will need to be done at specific locations so that Link can then deflect an arrow off the orb to hit a switch.