Upon placing an eye of ender in every end portal frame block of a specific portal, the portal activates, creating 9 end portal blocks inside the frame, and allowing the player to access the End. If the frame is destroyed, the portal blocks will still operate. In Creative mode, the player can create their own portal but it will only activate if the final eye is inserted into a block which was placed with the player standing inside the ring. The eyes can not be removed from the portal blocks.
Player-made portals may be created adjacent to one another, sharing blocks. However, if they are sharing anything except the corners, the last-placed eye of ender may not be in a 1 block diagonal to or up to 2 blocks adjacent to any frame block not belonging to that portal. They may, however, be freely stacked vertically.