Abstract: An adjustable knuckle joint device for folding ladders includes in combination: a first coupling member having a first circular junction portion provided with an annular flange and a plurality of openings and bulges therein and a first elongate joint portion extending at an angle from the circular junction portion; a second coupling member having a second circular portion with a flat top surface being movably connected to and in bearing contact with the first coupling member, and a second elongate joint portion extending at an angle from the second circular junction portion; a straight axle fitting pivotally connecting the first and the second circular portions together; and a snap catch positioning assembly operatably fixed on the second elongate joint portion of the second coupling member in conjunction with the first circular junction portion. By manually operating the snap catch positioning assembly, a simple, secure and safe adjustment of both coupling members relative to one another results.