Position and lightly clamp the tailgate frame to the trailer side keeping the top of the tie rails flush. 

Centralise the tailgate frame between the end uprights, double check that the tie rails are level and clamp tightly.

Slide the hinge pipe onto the pins and try to centralise the pipe vertically with the pin and tack weld the hinge pipe to the trailer.

Once all hinge pipes have been tack welded, release the clamps and operate the tailgate.

Check for any stiffness or misalignment and readjust the hinge pipes as required for a smooth tailgate action.

Fit the anti luce drop lock onto the drop lock tube (see below) and centralise the anti luce within the latch plate hole.

Level the tube and tack weld the drop lock tube to the side upright.

Again, check the action of the tailgate before fully welding.

Remove the tailgate from the trailer and fully weld together.