Recent interpretations of the eastern part of the triangle zone, at the front of the Canadian Rocky Mountain thrust belt, as a low-taper intercutaneous wedge imply that the upper and basal decollements of the wedge formed as subparallel and coeval structures with opposite senses of displacement. Previous theoretical models of frontal orogenic structures are difficult to apply to the low-taper intercutaneous wedge, because these models do not fully consider the effects of high and fluctuating pore-fluid pressures, anisotropic rock properties, and the dynamics of fault propagation. Concepts derived from the theoretical models as well as from recent studies of modern accretionary wedges, are integrated into a model which allows and explains opposing shear senses on coeval, yet subparallel shears. A blind foreland-directed thrust fault, the basal decollement, propagates from the deformation belt into the foreland. The decollement propagates into the "stable" region, where mean and differential stresses are too low for new faults to initiate. A zone of high pore-fluid pressure surrounds and precedes the migrating decollement tip. At the low differential stresses envisioned for this "stable" domain, the vertical orientation of the minimum effective stress, subhorizontal bedding anisotropies, and high pore-fluid pressure together promote horizontal extensional failure above the tipline of the decollement. Since this new failure plane is above the original decollement, it starts to accommodate the movement on the foreland-directed decollement by hinterland-directed displacement, thereby becoming the upper decollement. Once it has formed, this extensional fracture or zone behaves as an essentially frictionless surface, across which shear Stresses cannot be transmitted. As foreland-directed movement on the basal decollement continues, this free surface starts to glide, accommodating the tectonically driven movement along the basal decollement, and becoming the upper decollement. The upper decollement propagates towards the foreland, and back towards the hinterland, where it may cut up-section to break to surface as a backthrust. Little net slip can be accomplished until the basal and upper decollements have been linked. Once a linking ramp is formed, insertion of the wedge commences and strata in the foreland are delaminated.