Blind faults are documented from 20 thrust systems throughout the world. They occur as single faults, sets of faults, or entire thrust systems. The overlying cover responds to the formation of the blind system by backthrusting, coupling, forethrusting, and deposition. The relative importance of the first three responses for pretectonic cover is represented in a ternary backthrusting-coupling-forethrusting diagram. Pretectonic cover of blind systems deforms by either a combination of coupling and forethrusting or a combination of backthrusting and coupling.