Abstract: A foldable boom assembly including a hinge with inner and outer parts attached to inner and outer boom sections, respectively, permitting relative rotation of the inner and outer boom sections about a pivot axis. The outer end of the outer boom section swings rearwardly about the pivot axis upon contact with a foreign object. After passing the object, the outer boom section automatically returns to its original position. The outer boom section is capable of being folded to a position parallel to the inner boom section. A stop lug is located on one part of the hinge opposite a slot on the other part of the hinge. A movable plate is located on the same part of the hinge as the slot and is attached at a point above the slot such that the force of gravity causes the plate to cover the slot to cause the folding of the boom to be stopped at an intermediate position by contact between the stop lug and the plate.