  Certain Friedrichs systems can be posed on Hilbert spaces normed with a graph
norm. Functions in such spaces arising from advective problems are found to
have traces with a weak continuity property at points where the inflow and
outflow boundaries meet. Motivated by this continuity property, an explicit
space-time finite element scheme of the tent pitching type, with spaces that
conform to the continuity property, is designed. Numerical results for a model
one-dimensional wave propagation problem are presented.
