Abstract: A fastening assembly comprises a first internally open member such as a collar, and a second internally open member such as a bifurcated plug which is slidable realative to the collar to an assembled position in which the plug is located at least partially within the collar, at least one protrusion provided between the collar and the plug causing the plug to be deformed when in said assembled position, so as to create at least one inwardly directed jaw or fang for use in fastening engagement with a workpiece such as an externally threaded stud located at least partially within the plug, the advantage being that the amount of driving force which is transmitted in the driving direction to the stud through means of the fastening assembly can be minimized, so that the fastening assembly can have a knock-on/screw-off capability even if the stud is resiliently mounted on compressible foamed material.