Ball

Balls are traps that appear in the Eastern Palace and Eastern Temple of and  respectively.

Characteristics
Balls are launched from huge openings in dungeon walls and careen down corridors and across rooms. They will either appear in an endless and varied stream from a larger opening or are fired one after the other from smaller ones. Multiple launch points can lead to a lot of confusion as Link is forced to dodge and weave between the continuous assault of the giant metal traps. Larger openings can also occasionally launch Gargantuan Balls.

In Four Swords Adventures it is possible and sometimes necessary to avoid the balls by traveling to the Dark World.

Gargantuan Ball
Gargantuan Balls are particularly huge steel boulders that often appear at the end of a stream of smaller Balls. If Link has not progressed far enough down a corridor to escape to reach a point of safety, these huge Balls will be impossible to avoid and crash straight into him. In, these Balls will also sometimes fall down from above when certain switches are hit. They will then chase the four Links with apparent sentience, or possibly some kind of magnetism, and constantly hound them even down to lower floors. The only way to escape the giant metal menaces is to pass through a small passageway to escape and return to a higher floor.

Trivia

 * Gargantuan Balls look very similar to Big Steelies in Super Mario World.