Abstract: A direction controlling mechanism for an extendible boom forklift or the like controls the direction of movement of a predetermined point, such as a fork section connected to the distal end of the boom sections, relative to the forklift frame during retraction or extension of the boom members. The direction controlling mechanism is disposed between the proximal end of the boom sections and the main frame section of the forklift. The direction controlling mechanism includes an extendible member disposed between an upper shaft provided on the boom sections and a lower shaft provided on the vehicle frame. The length of the extendible member can be fixed during retraction or extension of the booms, and a driving mechanism moves the fixed length extendible member along the upper and lower shafts.