In the manga, the key is depicted to be an ordinary silver key with the crest of the Chisel stamped on its bow. In the anime, the key is still depicted as silver but is designed more intricately. The bow is circular and bears the crest of the Chisel on its center, colored green. The blade of the key ends in a simple design, similar to other silver keys.
While in possession of the key, a Celestial Spirit Mage may be able to summon the Chisel Caelum by reciting the quote, "Open Gate of the Chisel! Caelum!". This summons Caelum, a robotic Celestial Spirit that can be used as a sword or laser.