On Metru Nui, a small number of highly skilled Ta-Matoran earned the privilege of becoming mask makers. They were responsible for creating every Kanohi Mask of Power in the city, from the ones worn by Matoran to the Great Masks worn by Toa. Kanoka disks were used to make masks. There were two methods used to make Kanohi masks. In one method, a Matoran took a disk, melted it down, and poured the molten protodermis into a mask mold. After it cooled, it was removed from the mold, and any flaws were pounded out by the mask maker. A skilled crafter could spend many days at his forge trying to a get a mask just right. In the other method, a mask maker combined two or more Kanoka disks into one. He then carved the Kanohi from the disk using a mask-making tool, which resembled a small torch. Combining Kanoka disks allowed the mask maker to create new mask powers. After a mask was done, it would go to any one of a number of places. If it was a Noble or Great Mask, it was sent to Ga-Metru and placed in the Great Temple. If it was a Matoran mask, it was sent to Po-Metru for finishing and distribution. If the mask was flawed in some way, it was sent to the protodermis reclamation yard in Ta-Metru to be melted down.
Disks found to be of the right purity and power level were forged into Masks of Power.
No matter how many hours of work had gone into a mask, a single, tiny flaw could ruin it. Then it would be transported to the Protodermis Reclamation Center, to sit on top of a pile of other broken, useless masks until it could be fed to the furnace and melted down. A flawed mask could look perfect to the naked eye, its flaws visible only to a truly skilled crafter.
Nuhrii once fantasized about having a Mask of Power named after him, suggesting that masks may have been named after certain individuals.
Vakama had spent his whole life working alone at his forge, crafting protodermis into Matoran masks and Masks of Power. It required patience, skill, and dedication.
On Metru Nui, Kanohi Masks of Power were made from Kanoka disks. Kanoka with power levels 1 to 6 were made into Matoran masks, because the power leeched away during the mask-making process. Power level 7 disks were made into Noble Masks of Power. Power level 8 disks were made into Great Masks of Power like those worn by Toa.
The Kanoka disks of the winning teams of akilini tournaments were immediately transported to Ta-Metru to be turned into Kanohi masks. This was considered to be a great honor by Matoran athletes.
To make a mask, Vakama would put a Kanoka disk in the forge, then wait for the fire to soften the disk. When the time was right, he took it out and began to shape it with his firestaff. Molten protodermis was the raw material that was fed into the forge to be shaped into disks, and later into masks, if the grade of disk was high enough.