An apparatus for stacking items (I) includes first and second pluralities of stacker shelves (22) extending towards each other in spaced and parallel operative sections and each moving along first and second endless paths. The stacker shelves (22) are switchable by a switch (350) between extended and retracted positions. The stacker shelves (22) in retracted positions in the operative sections are operatively spaced from the item (I) received on the corresponding stacker shelves (22) in extended positions. In preferred aspects, the stacker shelves (22) are slideable relative to first and second plurality of carriers (310) carried along the first and second endless paths by roller chains (304). The switch (350) switches a cam follower (328) on each of the stacker shelves (22) into one of first and second cam tracks (342, 344) as the stacker shelves (22) enter the operative sections of the endless paths.