Abstract: A novel safety platform for use in a vertical shaft such as a manhole. The platform comprises a pair of support beams with the ends of each support beam mounted in the wall of the shaft. At least one panel extends across the shaft and bridges the support beams with a novel wedge clip at one end of the panel to allow the panel to be opened or secured in the closed position. A novel pivotting means is provided at the other end of the panel which pivotally secures the panel to the opposite support beam. The platform may be installed easily with fewer problems than the prior art yet provides increased safety factors for the user.

Abstract: An improved method of manufacturing a concrete manhole casing and plugs for use therein. The method comprises fabricating a form for the manhole and securing a plurality of retractable arbors on the inside thereof. The arbors are extended through the form and a sealed plug is inserted on the end of each arbor. The concrete is poured into the form; vibrated and compacted. The arbors are withdrawn leaving the sealed plugs in place. The plugs carry a threading on their periphery and a novel locking structure on the inside surface.