Supply boxes are a recurring source of items found throughout the game. There are seven varieties of boxes — one for each of the seven main Unite Morphs — and they can only be opened by interacting with them using the corresponding Unite Morph.
Supply boxes are highly unique among all item sources, not for their more involved methods of obtaining their item, but because of the fact that new boxes will appear in previously completed levels after obtaining the Unite Morph necessary to open them: this means that many items contained in a box cannot normally be obtaining during your first playthrough of a level, rewarding replays and continued exploration.
- See also: Items
Types of Supply Box[]
Unite Hand[]

Red Unite Hand Boxes are opened by using Unite Hand to turn the hand-crank on top.
Unite Sword[]

Blue Unite Sword Boxes are opened by attacking the box using Unite Sword, which will cut off the chains holding it shut. This can also easily be done using a Multi-United Sword.
Unite Gun[]

Green Unite Gun Boxes are opened simply by shooting the box using any form of Unite Gun. The actual target is merely decorative, and doesn't actually have to be hit.
Unite Whip[]

Pink Unite Whip Boxes are opened by attacking the box with Unite Whip, which will pull off the spiked door.
Unite Whip Boxes are also notable for being able to damage you if you come in contact with the spikes.
Unite Hammer[]

Yellow Unite Hammer Boxes are opened by striking the button on top using Unite Hammer, which is most easily done by executing the prompt that appears when approaching one, but they can also be opened with a very precise attack or even a Multi-United Hammer.
Unite Claw[]

White Unite Claw Boxes are opened by switching to Unite Claw and pulling the doors apart by button mashing.
Unite Bomb[]

Purple Unite Bomb Boxes are opened by slowing them using Unite Bomb, which will stop them from spinning and open its doors.
Unite Bomb Boxes are also notable for being able to damage you if you come in contact with one while it's still spinning.