  Jamming phenomena on a square lattice are investigated for two different
models of anisotropic random sequential adsorption (RSA) of linear $k$-mers
(particles occupying $k$ adjacent adsorption sites along a line). The length of
a $k$-mer varies from 2 to 128. Effect of $k$-mer alignment on the jamming
threshold is examined. For completely ordered systems where all the $k$-mers
are aligned along one direction (e.g., vertical), the obtained simulation data
are very close to the known analytical results for 1d systems. In particular,
the jamming threshold tends to the R{\'e}nyi's Parking Constant for large $k$.
In the other extreme case, when $k$-mers are fully disordered, our results
correspond to the published results for short $k$-mers. It was observed that
for partially oriented systems the jamming configurations consist of the blocks
of vertically and horizontally oriented $k$-mers ($v$- and $h$-blocks,
respectively) and large voids between them. The relative areas of different
blocks and voids depend on the order parameter $s$, $k$-mer length and type of
the model. For small $k$-mers ($k\leqslant 4$), denser configurations are
observed in disordered systems as compared to those of completely ordered
systems. However, longer $k$-mers exhibit the opposite behavior.
