Abstract: An exemplary knuckled, hydraulic-actuated stacking conveyor is disclosed for conveying and stacking particle-type materials, such as aggregate, slag, sand, coal, or the like. The conveyor includes inner and outer boom sections vertically supported by an intermediate support structure that does not extend vertically above the hinged or pivotal interconnection of the boom section. A constant length link support is provided for substantially preventing sagging of the preferred two-piece, telescoping hydraulic extension member that raises and lowers the outer boom structure.