When lecturing on the subject of his new invention, Abraham Wivell used a series of scale models. To operate this fire escape, the fly ladder was swung into position by means of ropes and access to the main ladder was obtained by opening the hinged section of the fly. A rescued person could be passed down the canvas chute beneath the ladder. The Lattice Girder Extending Escape, which was patented by James Shand in 1880, eventually superseded Wivell's ladder.