The ark was a small coffin-shaped device with an image of an Eygptian eye on its surface with Scarab Combination Locks on the corners. Once the image was rotated, the internal bomb was capable of being seen, which resembled a circular shaped device with Goa'uld writing on the sides indicating the time. The centre contained a light greenish glass dome.
The sides of the ark contained slots through which a user was capable of accessing the internal control crystals. However, improper use of the crystals was capable of either increasing the time until detonation (by tampering with the red control crystal), or bring about a premature detonation. Scans can reveal that the device contains a ten-pound block of Naquadah.
It was incapable of being moved as it possessed sensors capable of detecting any attempt to relocate it, which would have resulted in detonation. Furthermore, the removal of the power regulation crystal from the control board can result in an explosion as well. Inputting the proper access code however, was capable of deactivating the bomb.
Sekhmet held one such device during her time on Earth before she was placed in a Stasis jar. It along with several other artifacts were recovered by Napoleon and later by the Nazis. During this time, it eventually made its way to the rogue branch of the NID.
It was activated by the genetic personality of Sekhmet that resided in the girl Anna and was going to detonate in sixteen hours. SG-1 minus Colonel Jack O'Neill attempted to deactivate the Ark as it threatened to devastate a city on Earth at the time. Bill Lee was finally able to stop the ark from exploding by using Anna's drawings to input the deactivation code. (SG1: "Resurrection")