  In this paper, we define dual geodesic trihedron(dual Darboux frame) of a
spacelike ruled surface. Then, we study Mannheim offsets of spacelike ruled
surfaces in dual Lorentzian space by considering the E. Study Mapping. We
represent spacelike ruled surfaces by dual Lorentzian unit spherical curves and
define Mannheim offsets of the spacelike ruled surfaces by means of dual
Darboux frame. We obtain relationships between the invariants of Mannheim
spacelike offset surfaces and offset angle, offset distance. Furthermore, we
give conditions for these surface offsets to be developable.
