They were fashioned as flush doors, the jambs invisible to the eye, and matched so perfectly with the mountain rock that when closed the Doors could not be seen. The slabs were made by Narvi out of a grey material stronger than stone, and inlaid by Celebrimbor with
ithildin, which could only be seen in starlight and moonlight.
When visible, the fine silver-like inlay showed a hammer and anvil (the emblems of
Durin), a crown and
Seven Stars (probably
Durin's Crown), two trees surmounted by crescent moons, and a single star (the emblem of the
House of Feanor). On the top left and right corners there were the
tengwar Calma (C) and
Óre (N) standing for Celebrimbor and Narvi.
The inscription on the
archivolt read:
"Ennyn Durin Aran Moria. Pedo Mellon a Minno. Im Narvi hain echant. Celebrimbor o Eregion teithant i thiw hin."
"The Doors of Durin, Lord of Moria. Speak, friend, and enter. I, Narvi, made them. Celebrimbor of Hollin drew these signs."
The inscription stated the password that would cause the Doors to swing open.
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From the inside the Doors could be opened by simply pushing against them. However, it usually took the thrust of two to do so. When Moria was inhabited by the Dwarves they kept doorwards inside who would help open the Doors and see that only those with permission could pass.