To verify user subroutine GAPCON, the thermal interface properties verification tests of “Thermal properties,” Section 2.3.1, are repeated using the user subroutine to specify gap conductance values. Results match for both methods of specifying gap conductance values. The tests are set up as cases of uniform one-dimensional heat flux using two- and three-dimensional elements. For the three-dimensional analyses, the temperature results are identical for all nodes located on a particular plane along the direction of heat flow. These include nodes 1–7 at plane A, nodes 101–107 at plane B, and nodes 201–207 at plane C. A steady-state heat transfer analysis is performed in several increments in all cases. Particular values (gap clearance, predefined field variables, etc.) vary during the solution, which in turn influence the conductivity across the interface and, thus, the solution. These values are passed into user subroutine GAPCON where an appropriate value of gap conduction is specified, thus affecting the temperature solution.