  The impact of liquid drops on a rigid surface is central in cleaning, cooling
and coating processes in both nature and industrial applications. However, it
is not clear how details of pores, roughness and texture on the solid surface
influence the initial stages of the impact dynamics. Here, we experimentally
study drop impacting at low velocities onto surfaces textured with asymmetric
(tilted) ridges. We define the line-friction capillary number $Ca_f={\mu_f
V_0}/{\sigma}$ (where $\mu_f$, $V_0$ and $\sigma$ are the line friction, impact
velocity and surface tension, respectively) as a measure of the importance of
the topology of surface textures for the dynamics of droplet impact. We show
that when $Ca_f \ll 1$, the contact line speed in the direction against the
inclination of the ridges is set by line-friction, whereas in the direction
with inclination the contact line is pinned at acute corners of the ridge. When
$Ca_f \sim 1$, the pinning is only temporary until the liquid-vapor interface
reaches to the next ridge where a new contact line is formed. Finally, when
$Ca_f\gg 1$, the geometric details of non-smooth surfaces play little role.
