Abstract: A work platform for buildings having a guard rail having, at one end, a movable part pivotally mounted for movement about a horizontal axis between a working position and an upright safety position the guard rail including a mechanism carrying switch means arranged in the working position of the said movable part to be positioned to contact a member on an adjacent platform to control a circuit to stop the platform moving in a vertical direction and the movable part being controlled by said mechanism which also positions said switch means to prevent the platform passing one another when the end frame movable part is in any position except the safety position.