at 30 for the forward crank arms 23 and 32 for the rear pair of crank arms 25 the saw box along its bottom edge 34 is provided with downwardly opening recesses 36 at the forward side of the box 10 and 38 adjacent the rear face of the box 10 each recess includes a bearing ring 37 to retain the respective rod 30 in its respective recess 36 it will be understood that the rods 30 and 32 extend across the width of the box 10 to the opposite side to register with corresponding aligned recesses provided on the opposite side of the box 10 from that shown in fig4 to achieve movement preferably a hydraulic cylinder and piston 60 is employed with the piston connected by a rod 60 to the linkage arm 22 the actuation of the piston 60 will be controlled by a computer and which will operate a valve box 66 the computer will be connected to sensors which will detect the vertical height of the cant passing at a point upstream of the saw box 10 a number of suitable sensors mechanisms are available on the market for this purpose the piston 60 will then be fed with fluid to move the linkage arm 22 either leftward to lower the saw box 10 in the direction of arrows 56 to the position shown in fig6 or rightward to move the saw box 10 to the position shown in fig7 it will be understood from fig1 that the saw box 10 includes the drive motors 95 95 u2032 guard 95 and associated housing with the foregoing arrangement the saw box of the.