Folding ladder

A folding ladder having a pair of upright, parallel side rails and a plurality of cross rungs, each rung having horizontal pivots at its opposite ends hinging the rung respectively to the rails so as to enable the rails and rungs to function selectively in an open mode with the rails spaced apart and the rungs disposed horizontally or in a closed mode with the rails shifted vertically and swung closely together about the rung pivots to dispose the rungs in acutely angled relation to the rails, characterized in that each rail includes a top portion, a lower portion and an intermediate portion and at least the intermediate portion has a substantially semi-circular transverse section giving that portion the shape of a C as seen in plan, the rails being symmetrical and with the open sides of the Cs facing toward each other, each rung is a rigid element and the rung pivots and opposite ends of the rungs lie within the bight of the C, whereby, in the closed mode the intermediate portions of the rails complement each other to form a vertically elongated, hollow substantially cylindrical closed shell enclosing the rungs there within each rung pivot comprises a bearing block of semi-cylindrical section configured to nest within its associated rail, said block further having a gap therein facing the opposite rail, the proximate end of the end of the associated rung is received within the gap, a cross pin is carried by the block and passes through the received end of said rung and each rail having horizontally alined holes respectively coaxial with each cross pin and each block has coaxial portions projecting respectively into the associated holes.