Abstract: An axial force generating tool for applying a force on a structure positioned within a borehole is taught. The tool includes a housing (19) sized to fit within the borehole in which the tool is required to act; an outer seal (38) disposed about the housing and selected to create a seal between the housing and the borehole; an inner bore (32) through the housing including a seal to prevent flow from the inner bore out through the lower end; an opening (34) to the inner bore above the seal; a bracing means (36) for maintaining the housing against axial movement in the borehole once the housing is in a selected position within the borehole; a piston (27) mounted in sliding engagement wiht the housing for axial movement relative to the housing, the piston positioned to act between a pressure differential establishable between the inner bore and the borehole between the seal and the lower end to drive the piston axially relative to the housing; and a grapple connected to the piston for axial movement therewith.