When a key interfaces with the doorway, the correct combination will initiate the teleporter. Travelers must enter simultaneously, or be in physical contact, otherwise one may be missed. A glowing energy field encompasses the travelers, which snaps them away to a secluded sanctuary on the Utopian moon. (SG1: "Paradise Lost")
The only known key capable of activating the portal was formerly located in a pharaoh's tomb in Egypt. Harry Maybourne managed to acquire the key and have its writing deciphered, as well as the combination to open the doorway.
For the arch to work on the Utopian moon, three crystals must be highlighted in order to make a connection. The key must then be removed from its interface before the door will activate, keeping others from following if the user decides to travel with their key. (SG1: "Paradise Lost")