  We discuss the optimal spin bases for describing angular correlations in
single top quark events at the Fermilab Tevatron. We define spin bases that
exploit the fact that the top quarks are produced with 100% polarization along
the momenta of the d-type quarks in these events. For single top production
through an s-channel W boson, 98% of the top quarks have their spins in the
antiproton direction. For single top production via Wg-fusion, 96% of the top
quarks have their spins in the spectator jet direction. The direction of the
top quark spin is reflected in the angular correlations of its decay products.
