Basic types of thrusts recognizable in many orogens include: (1) foreland fold-thrust belt (and accretionary complex) thrusts, (2) Type C crystalline thrust sheets that detach along the ductile- (plastic) brittle transition in either continental or oceanic crust, and (3) Type F (fold-related) crystalline thrust sheets that are generated beneath the ductile-brittle transition by plastically shearing the common limb between antiforms and synforms. Spacing of thrusts in a foreland fold-thrust belt is determined by the thickness and shear strength of the dominant structural-lithic unit and by basement irregularities, facies changes, and the development of stress maxima that localize buckling instabilities. Displacement-length plots for the Canadian Rockies and Alberta Foothills, along with the Wyoming-Idaho-Utah thrust belt thrusts, plot on a linear curve. Appalachian foreland fold-thrust belt thrusts, however, plot on three curves that separate triangle zone thrusts from thrusts of small displacement from thrusts of large displacement. Type C sheets plot on a curve of positive slope separate from Alpine plastic Type F sheets, which plot on a curve of negative slope, because pure Type F sheets may involve a greater component of constrictional flow. Upper bounds for the size of thrust sheets are delimited by the thickness and strength of their strong components, the size of the orogen of which a thrust sheet is a part, and by other inherent properties of a deforming wedge. Foreland fold-thrust belts contain thrust sheets that reach their maximum size as a function of the thickness and along-strike continuity of structural-lithic units. The maximum size of Type C sheets may be attained by the constancy of the geothermal gradient over a wide area during continent–continent collision.