Recent ideas about the analogue for a three-phase contact line of the Gibbs adsorption equation for interfaces are illustrated in a mean-field density-functional model. With d τ the infinitesimal change in the line tension τ that accompanies the infinitesimal changes dμi in the thermodynamic field variables μi and with Λi the line adsorptions, the sum [image omitted], unlike its surface analogue, is not 0. An equivalent of this sum in the model system is evaluated numerically and analytically. A general line adsorption equation, which the model results illustrate, is derived.