  We propose an equation that describes the shape of the driven contact line in
dynamics in the presence of an arbitrary (possibly random) distribution of the
surface defects. It is shown that the triple contact line depinning differs
from the depinning of interfaces separating two phases; the equations
describing these phenomena have an essential difference. The force--velocity
dependence is considered for a periodical defect pattern. It appears to be
strongly nonlinear both near the depinning threshold and for large contact line
speeds. This nonlinearity is comparable to experimental results on the contact
line depinning from random defects.
