Tollan phase-shift technology allows objects to pass through solid matter. A Tollan device worn on the wrist enables a person to pass through walls. Trinium is required to house any device that generates the phase-shift technology. The Goa'uld forced the Tollan Curia to build weapons of mass destruction using phase-shift technology, which would enable them to penetrate solid matter prior to detonation. The Goa'uld intended to use these weapons to penetrate Earth's iris, however the weapons, and Tollana, were destroyed by the Goa'uld when the Tollans refused to cooperate.
Cross Reference: Alternate Dimension, Invisibility, Tollans, Trinium
Episode Reference: Enigma, Pretense, Shades of Grey, Between Two Fires