The brace that will support the upper mounts of the rear damper and the upper pivots of the Shaw Link.  The big bolt at the top center of the picture goes up through a hole in the end bracket of the cross brace, through a hole in the frame rail, and meets with the threaded backing plate installed in a similar, but larger hole in the trunk floor.  This was kind of difficult, since the cross brace was built to Ford chassis specifications, but the chassis that roll off the assembly lines fo not often measure up, so there is always some misalignment.
photo of installed cross brace 

Note the fuel return line cut that was cut short (after it was crimped in the first attempt to move it out of the way of the cross brace).