The present invention utilises impact-driven fastener (1) having a twisted body having: a common axial core (2) a protruding helix (3) and a trailing elongate lost-end driving shank: (4) of reduced radial diameter. The fastener incorporates two or three loosely wound loosely wound thread-cutting blade-like helical projections (5) extending radially from a solid axial core (2). These blade-like projections (5) are inclined upon a sweeping helical angle (8) of less than 42° to the longitudinal axis (9) of the core (2). The elongate shank (4), which carries no swept angle thread-cutting blades, has a reduced cross sectional diameter that is approximately one half or less of a cross-sectional circumscribed diameter (7) of a protruding helix (3), from which it extends coaxially, such as to fit into and cooperate with a driving adapter (21) having a hollow leading end (24), said leading end of a driving adapter having an external diameter that is less than a cross-sectional circumscribed diameter (7) of the fastener (1).