Stones of Time are items from The Legend of Zelda: Ocarina of Time. These bluish blocks are carved with the same design that appears on the Door of Time. Stones of Time appear in many locations throughout the land of Hyrule, though they are found primarily within dungeons. They are used either to block entrances or to provide a step for reaching high ledges.
If Link plays the "Song of Time" on his Ocarina of Time, the Stone of Time will move either to another location or to the other time frame. Sometimes, Navi will turn green and fly to a specific, empty location. Playing the "Song of Time" in these locations usually causes a Stone of Time to appear. These stones move back and forth between the seven years time whenever Link plays the Song of Time near them (though their spatial locations are apparently shifted).