The Box is constructed from a thick metal, most likely titanium. The top lid section is thicker than the bottom half, since it contains the Box's computer, locking mechanism, timer, and power source. The box can be opened by depressing the two locks on either side of the timer display at any time, unless the countdown timer is active. There is an outlet on the inside of the lid that can be interfaced with a computer to set the desired time increment, and three LCD screens allow for a maximum setting of 999 years. The Instructions can be placed inside the box, over an engraved logo of the City of Ember, and a small switch on the side can be pressed to open the drawer that contains the Holocard.
The Box was filled and locked by the Builders at the beginning of Ember Year zero, and was passed down from mayor to mayor, until the year 153, when the mayor died before he could explain its function to his replacement. The Box was lost in a closet in the Yarn shop until the year 241, when it was discovered by 5-year-old Poppy Mayfleet. Poppy ate and tore several sections of the papers within. The remnants of the message were deciphered by Lina Mayfleet and Doon Harrow, who escaped the city through the river and sent a message to the people below, informing them of the world above. It is assumed the box was left behind in Ember.