A set of theoretical equations, assuming linearly elastic materials, has been developed that describes the stresses and displacements everywhere in a line-backpacking support system. It is assumed that the field stresses are applied to the system after the liner has been placed, and that the pressures due to the instability of the rock opening itself are not considered. Theoretical work is applicable to any number of concentric layers of material, thereby enabling one to handle underground situations where backpacking can be placed between liner and rock. Graphs showing the benefits and limitations of backpacking are given along with an example showing the effects of an ultrasoft layer of material surrounding the liner. These equations, where applied to existing field data, show good agreement with measured values, and they have also guided the design of field liner installations.