  By taking into account precursor films accompanying nanodroplets on
trapezoidal substrates we show that on a mesoscopic level of description one
does not observe the phenomenon of liquid-gas-substrate contact line pinning at
substrate edges. This phenomenon is present in a macroscopic description and
leads to non-unique contact angles which can take values within a range
determined by the so-called Gibbs' criterion. Upon increasing the volume of the
nanodroplet the apparent contact angle evaluated within the mesoscopic approach
changes continuously between two limiting values fulfilling Gibbs' criterion
while the contact line moves smoothly across the edge of the trapezoidal
substrate. The spatial extent of the range of positions of the contact line,
corresponding to the variations of the contact angle between the values given
by Gibbs' criterion, is of the order of ten fluid particle diameters.
