  We consider self-avoiding walks terminally attached to an impenetrable
surface at which they can adsorb. We call the vertices farthest away from this
plane the top vertices and we consider applying a force at the plane containing
the top vertices. This force can be directed away from the adsorbing surface or
towards it. In both cases we prove that the free energy (in the thermodynamic
limit) is identical to the free energy when the force is applied at the last
vertex. This means that the criterion determining the critical force -
temperature curve is identical for the two ways in which the force is applied
and the response to pushing the walk is also the same in the two cases.
