The thread 4, intended to form a carcass reinforcement, is laid in continguous hoops on a rigid core 1 by a system with at least two oscillating arms transporting an orifice 6 so as to enable it to pass over a core 1 and thus lay adjacent hoops. The method comprises the steps of heating the lithium metal powder to above its melting point to provide molten lithium metal, dispersing the molten lithium metal, and contacting the dispersed molten lithium metal with a phosphorous-containing compound to provide a substantially continuous protective layer of lithium phosphate on the lithium metal powder. The bypass flow passage incorporates a depressible region which is depressible to open or close the bypass flow passage. The lower surface of the anchor head may be angled to further simplify the task of feeding a surgical needle through the anchor hole after the anchor is seated into bone.