  Using the standard symmetry technique for applying boundary conditions for
free slip and flat walls with corners will lead to flow leak through the wall
near corners (violation of no penetration condition) and a corresponding error
in prediction of pressure. Also, prescribing a state at the corner as a
boundary condition is not possible. In this paper, a method for tackling the
`corner point state' problem is given and modifications to the standard
symmetry technique are proposed to mitigate flow leak near the corner. Using
this modified symmetry technique, numerical solutions to the Euler equations
for flows over forward facing and backward facing step are computed employing
the Shu-Osher conservative finite difference scheme with WENO-NP3
reconstruction (with a formal order of accuracy in space of 3), Lax-Freidrichs
flux splitting, and TVD-RK3 time discretisation. It is shown that using this
modified symmetry technique leads to mitigation of flow leak near the corner
and a better prediction of shock structure even on coarse meshes.
