Abstract: A portable folding ladder comprising a plurality of U-shaped modules having a rung and two vertical portions, the modules movable connected to each other, and when opened becoming progressible narrower as they approach the top of the ladder, when folded the narrower modules fitting inside of the next wider modules and locking means to lock the modules in a rigid manner which when the ladder is extended and open.

Abstract: A portable and convertible ladder comprising a series of u-shaped modules each movably connected to the other by hinge means, said modules having progressively decreasing widths as they approach the top of the ladder when in an open mode, said modules having a base or rung portion and upright sections, each module having locking means movably positioned in their lower portion, and adapted to form a substantially rigid ladder when in an open mode, each module except for the uppermost module having hinge means at substantially the upper portion of said upright sections, said locking means having a locking member positioned in said lower portion adapted to fit and mate with complimentary male or female member positioned in an adjacent portion of said upright sections, at least a section of the wider of said modules overlapping at their upper vertical portions with the bottom portions of the next adjacent narrower modules, and said locking means and said module hinge means provided in said overlapping portions.