are provided for transferring bulldozing loads exerted on the levers 21 through the lower blade in either operating mode directly into the push arms 40 so as to relieve such loads from the jacks 30 such stoppers are also effective in relieving the jacks of impact loads in the event the blade mechanism is dropped from its maximum height to the ground an alternate embodiment of the present invention is illustrated in fig9 and 10 which is substantially identical to the preceding embodiment except for the following distinctions the first distinction includes the use of two pairs of lower braces or links 45 39 which while being similar to the single pair of links 45 of the preceding embodiment are mounted in a somewhat different manner therefrom the links 45 39 are individually mounted on the opposite sides 40 39 of each of the push arms 40 by pins 38 39 the other ends of such links are pivotally mounted by pins 20 39 to a pair of aligned brackets one of which is shown at 19 39 carried on the lower blade 12 another difference of this embodiment is in the construction of the stoppers 50 39 which includes an upper edge or face 50a 39 a forward edge or face 50b 39 and a lower edge or face 50c 39 the upper faces 50a 39 are disposed for impingement against the respective longitudinal edges of the side boards 21a and 21b of the levers 21 when in its pulling attitude fig1 whereas the forward faces 50b 39 are disposed for impingement against such edges when the lever is in its pushing attitude fig9 as in.