  We consider the set of pairs of orthogonal vectors in Hilbert space, which is
also called the cross because it is the union of the horizontal and vertical
axes in the Euclidean plane when the underlying space is the real line.
Crosses, which are nonconvex sets, play a significant role in various branches
of nonsmooth analysis such as feasibility problems and optimization problems.
  In this work, we study crosses and show that in infinite-dimensional
settings, they are never weakly (sequentially) closed. Nonetheless, crosses do
turn out to be proximinal (i.e., they always admit projections) and we provide
explicit formulas for the projection onto the cross in all cases.
