It is a small shock absorber like item that holds the rear

door of a wagon in the open position. When you close the rear door

you hear a swish sound -- that is the tailgate cylinder

compressing. On an 855/V70 they are attached at the top near the

hinges and are mounted in the roof area (parallel to the ground).

Looking at the doors hinges you can see one end of the cylinder.

When they wear the rear door will not stay open -- it basically

closes under its own weight.

Most sedans have the same thing and they are typically easier

to see in the trunk of a sedan. Hmmm, wonder if the sedan and

wagon parts are interchangable?