  Explorations of the order-disorder transformation in vortex matter in single
crystals of tetragonal structured (c/a $\sim$3) borocarbide superconductors,
$YNi_2B_2C$ and $LuNi_2B_2C$, reveal that vortex arrays experience different
effective pinning in different crystallographic directions. We surmise that
correlation exists between the large anisotropy in effective pinning/disorder
and the differences in the (local) symmetry transition from rhombohedral to
(quasi) square vortex lattice(VL). For field along high symmetry directions,
like, c-axis and ab-basal plane, the VL symmetry is close to square and the
ordered state spans a large field interval. When the field is turned away from
the c-axis towards ab-plane, at intermediate angles, the region of ordered
state shrinks, in response to enhancement in effective pinning. At such
intermediate angles the symmetry of the VL would be far from ideal triangular
or square.
