This is Hydraulic Tack Welding Jig (common) for all Chassis model ( All wheel base 2515, 2815, 3315, 4240, 4760 & 5100). So basically this jig clamps the the Chassis Assembly first with Resting, Clamping Brackets and Expander Elements all located in the Jig. All Clamping Brackets and Expander Elements are Hydraulically operated. Then after the clamping comes welding of several chassis parts like in Front arear of chassis is FUPD Assembly , Damper Bracket, Cabin Mounting Bracket following Cross Member Assemby #1, #2 & #3 and then comes the Spare Tyre Mounting Brackets, Stopper Brackets Front and Rear, Rear Guard Bracket, etc.