Abstract: A safety system for a multi-story building under construction includes parallel, vertical stationary guide channels or tracks secured to the side of the building. Vertically moveable slide rails are slidably mounted within the guide channels. Cantilever struts extend diagonally upwardly and outwardly from connections with the slide rails. A safety net extends along the building with its outer edge anchored at the outer ends of the struts and with its inner edge anchored on the moveable slide rails. Vertical chains or cables are connected between the slide rails and a construction crane at the top of the building to lift the slide rails and net while in an extended condition to a new working position. Brakes acting between the slide rails and guide channels automatically release to enable upward movement and automatically lock to hold the net in the new working position.