  Thin shell wormholes are constructed by joining two asymptotically flat
spacetimes along their inner boundaries. The junction conditions imposed on the
spacetimes specify the equation of state of the matter called thin shell
distributed along the joined boundaries. Barcelo and Visser (2000) reported
that spherically symmetric thin shell wormholes have their shells, namely the
wormhole throats, on the photon spheres if the wormholes are $Z_2$-symmetric
across the throats and the shells are of pure tension. In this paper, first, we
consider general joined spacetimes (JSTs) and show that any $Z_2$-symmetric
pure-tensional JST (Z2PTJST) of $\Lambda$-vacuum has its shell on a photon
surface, a generalized object of photon spheres, without assuming any other
symmetries. The class of Z2PTJSTs also includes, for example, brane world
models with the shells being the branes we live in. Second, we investigate the
shell stability of Z2PTJSTs by analyzing the stability of the corresponding
photon surfaces. Finally, applying the uniqueness theorem of photon spheres by
Cederbaum (2015), we establish the uniqueness theorem of static wormholes of
Z2PTJST.
