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. Combined with advances in whipstock and milling technologies, the digital component is enabling operators to plan and conduct sidetracking operations with greater flexibility, precision, and efficiency—important objectives considering the variety of scenarios where the procedure is used. 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.