This chapter presents approximate attacks on logic locking, namely AppSAT and Double-DIP. Approximate attacks target compound logic techniques and reduce a compound technique (comprising a low corruptibility technique and a high corruptibility technique) to the low corruptibility technique. AppSAT augments the basic SAT attack with random queries at regular intervals; it terminates when the computed OER is below a certain threshold. Double-DIP makes use 2-DIPs that eliminate at least two incorrect key values per 2-DIP; the attack terminates when 2-DIPs can no longer be found. The effectiveness of the approximate attacks cautions against naive integration of logic locking techniques. This chapter is about approximate attacks on logic locking. Approximate attacks target compound logic locking techniques, reducing the compound technique to its constituent low-corruptibility technique. Section 6.1 introduces compound logic locking techniques that paved the way for the emergence of approximate attacks. Section 6.2 elaborates on the operation of the AppSAT attack . Section 6.3 describes how Double-DIP attack  works and how the attack methodology differs from that of the AppSAT attack.