This style comprises a greater variety of forms than all the others
combined, it requiring the least exertion to move the box up or
down. The weight of the camera box when placed on the stand top is
counterbalanced by weights which rest upon a shelf attached to
cords, which pass over pulleys and downwards, to be fastened to
uprights which support the top; when properly balanced it requires
only a touch of the hand to raise the box or to lower it.