Abstract: A fastener for fastening at least two work pieces together comprises a body and a pin. The body has a head, a shaft extending from the head and an open hollow core extending into the shaft. The shaft has a retaining means spaced from the head to accommodate the work pieces. The retaining mechanism has a contracted configuration where it is sized to pass through holes in the work pieces and an expanded configuration where it is expanded in size or spacing such that the shaft is unable to be removed from the holes in the work pieces. The retaining mechanism defines a constriction in the core at which the core has a first width when the retaining mechanism is in its contracted configuration. The pin is locatable in the core. The pin has a least a first portion with an external width greater than the first width of the core.