1. A DEVICE FOR INSTALLING AND REMOVING A TRUSS FRAME HAVING UPPER AND LOWER BOOMS AND USED IN THE CONSTRUCTION OFO BRIDGES, REMOVABLE HANGARLIKE STRUCTURES OR THE LIKE, SAID DEVICE COMPRISING AT LEAST ONE END BEARING UNIT COMPOSED OF TWO MEMBERS, A BEARING PLATE ADAPTED TO BE RESTED ON A STATIONARY SUPPORT, MEANS PIVOTALLY CONNECTING ONE OF SAID MEMBERS TO ONE END OF THE UPPER BOOM OF SAID TRUSS FRAME AND TO SAID BEARING PLATE SO AS TO BE PIVOTABLE RELATIVE TO AND WITHIN THE PLANE OF SAID FRAME AND RELATIVE TO SAID BEARING PLATE, SAID ONE MEMBER COMPRISING SEVERAL PARTS, AND MEANS FOR ADJUSTING SAID PARTS RELATIVE TO EACH OTHER TO VARY THE TOTAL LENGTH OF SAID ONE MEMBER.