The modular whipstock sidetracking system delivers quality, full-gauge windows for exiting steel casing. Sidetracking, the long-proven technique of setting a whipstock to exit an original wellbore to tap an alternate production zone or bypass a downhole obstruction, is relying on digital technology to enhance performance in increasingly challenging formations and complex well trajectories. In open holes where toolstring failures have occurred, whipstocks, often are set to sidetrack around a lost bottomhole assembly (BHA) to recover the drilling program. In cased holes experiencing reservoir depletion, a whipstock system can perform a slot recovery, drilling ahead to a different part of the reservoir using as much of the original wellbore structure as possible. Sidetracking also enables slot recovery on offshore platforms, which are restricted by the number of well slots from which to drill.