Strike-slip fault systems often contain zones of steep imbricate faults geometrically similar to imbricate fans and duplexes in dip-slip, thrust and normal, fault systems. They are evident in map view rather than in vertical sections. Examples of duplexes are cited from both active and ancient systems and from theoretical and physical models. Duplexes may form at bends on strike-slip faults by a process kinematically analogous to the sequential imbrication of ramps on dip-slip faults. However some may form, and many may initiate, as non-sequential ‘Riedel’ fractures at fault offsets or on straight fault segments. This process is more marked than in dip-slip systems where primary anisotropy such as bedding exerts more control on fault geometry. Strike-slip duplexes may be shunted along the fault system parallel to the regional slip vector. However, duplexes or individual horses will usually also move up or down perpendicular to the slip vector because of the unconstrained upper surface to the fault system. These factors mean that no section through a strike-slip system should be expected to area balance. The faults of strike-slip duplexes and imbricate fans may root in kinematically necessary low-dip faults or may converge downwards and appear in vertical sections as flower structures.