An internal hinge for use with first and second members such as the front and back legs of ladders in which there is a generally tubular means having a first portion adapted to be inserted into an aperture in the first member and a second portion adapted to be inserted into a second aperture in the second member. The apertures are aligned and adjacent one another and in the first portion there are two peripheral slots opposite one another through which a rigid pin passes, the ends of the pin being fastened to the first member. The second portion has two aligned transverse apertures through which a second pin is passed from outside the second member. Other embodiments include detented slot means for allowing selected angular positions of the legs, non-round tubular means, three-pin versions allowing two members to pivot with respect to a third, etc. Other embodiments include plant stands, easels, saw-horses, collapsible tables and collapsible seats.