A ladder with extendible legs that may be individually and selectively, secured in the desired extent of protraction by a relatively uncomplicated locking mechanism. The locking mechanism may be incorporated in a ladder having at least a pair of support legs with an extension leg carried by, and slidable axially along, each support leg. A reaction surface is presented from each support leg. A pair of locking cam surfaces is also presented from each support leg. The locking cam surfaces are disposed in spaced opposition to each reaction surface. An engaging plate is presented from each of the extension legs. The engaging plate is slidably interposed between the reaction surface and the opposed locking cam surfaces. A locking member is, in turn, operatively disposed between the engaging plate and the opposed locking cam surfaces. Each locking member is movable along at least one of the locking cam surfaces selectively to wedge the engaging plate against the reaction surface in order axially to secure the extension leg at the desired position along the axial extent of the support leg. The locking member is also movable selectively to release the extension leg for axial movement along the support leg. A linking mechanism is provided to control movement of the locking member in order selectively to secure or release each extension leg for retraction and/or protraction.

This invention relates to a convertible step/extension ladder which allows to use one or more of extension sections with a basic A-shaped ladder frame. The extension sections are slidably mounted on legs of the frame through the use of housing/sliding rail arrangement on the legs of the frame and on the extension sections. When converted to an extension ladder, the basic frame portions are folded and locked in that position, while one extension section is moved along the frame portion to rest on the ground. If more than one extension sections are used, the second extension section is mounted on the opposite frame portion and extended upwardly, so that the basic frame portions form a middle part of the ladder.

An adjustable back leg assembly provides a step ladder of simple construction for convenient use on stairs and other sloping surfaces.

A folding ladder includes a hinge assembly having first and second ladder hinge plates each defining a plate opening and a plurality of locking slots. A housing is associated with the first ladder hinge plate and extends through the plate openings to provide a rotation axis for the plates, and the second plate is operable to rotate relative to the first plate about the rotation axis to selectively align slots of the first and second plates. A key outside the housing selectively engages aligned slots to selectively prevent rotation of the ladder hinge plates about the rotation axis and is operated by a manual rotation member. An extension ladder includes a pair of nested outer and inner ladder rails. Ladder rungs connected between and the inner rails define a plurality of supporting openings and the inner rails include outer bearing surfaces associated with the supporting openings. An extension latch mechanism having a pivoting dog is coupled to an outer rail and engages the supporting openings and outer bearing surfaces to support the ladder in an extended posision.