Leveling device for derricks

Claim 1

A JACK COMPRISING A FLAT ELONGATED PLATE-LIKE BASE, A PAIR OF WEDGE MEMBERS SLIDABLY DISPOSED ON THE UPPER SURFACE OF SAID BASE FOR MOVEMENT LONGITUDINALLY OF SAID BASE TOWARD AND AWAY FROM EACH OTHER, AN ELONGATED LIFT SECTION OVERLYING SAID WEDGE MEMBERS EXTENDING LONGITUDINALLY OF SAID BASE AND PROVIDED WITH OPPOSITELY INCLINED LOWER SURFACES, EACH OF SAID WEDGE MEMBERS HAVING AN INCLINED UPPER SURFACE COMPLEMENTARY TO AND IN SLIDING CONTACTING RELATION WITH ONE OF SAID INCLINED LOWER SURFACES OF SAID LIFT SECTION, MEANS SECURED BETWEEN SAID WEDGES FOR ADJUSTING THE DISTANCE THEREBETWEEN WHEREBY THE DISTANCE BETWEEN SAID BASE AND LIFT SECTION MAY BE VARIED, GUIDE MEANS ON THE UPPER AND LOWER SURFACE OF SAID WEDGE MEMBERS ENGAGING THE ADJACENT PORTIONS OF SAID LIFT SECTION AND BASE RESPECTIVELY AND RESTRICTING SLIDING MOVEMENT OF SAID WEDGE MEMBERS ALONG SAID BASE AND LIFT SECTION TO MOVEMENT LONGITUDINALLY THEREOF, AND THRUST BEARING MEANS RIGIDLY SECURED TO SAID BASE AND DISPOSED IN SLIDING CONTACTING RELATION WITH SAID LIFT SECTION PREVENTING LONGITUDINAL SHIFTING OF SAID LIFT SECTION IN ONE DIRECTION.