A fastener unit adapted to secure at least one board to a support, the fastener unit comprising: a spacer body defining a first fastener hole configured to receive a fastener having a longitudinal axis therein, the spacer body including a front surface, an opposing rear surface, a first side surface and a second side surface opposite the first side surface, the spacer body having a thickness extending from the front surface to the rear surface, the thickness intended to provide a preselected gap between a first board and a second adjacent board, a grip element joined with the spacer body, the grip element defining a second fastener hole aligned with the first fastener hole of the spacer body, the grip element extending forward and rearward of the spacer body and configured to fit in and engage a first groove defined by the first board, characterized in that: the spacer body includes a first resilient compression element extending outwardly from the first side surface of the spacer body and a second resilient compression element extending outwardly from the second side surface of the spacer body on opposite sides of a vertical axis of the spacer body, the vertical axis of the spacer body corresponding to the longitudinal axis of the fastener, wherein: the first and second resilient compression elements are configured to fit in the first groove and forcibly hold the spacer body in place adjacent the first groove during installation of the fastener; or the first resilient compression element is configured to be placed adjacent a first side of a joist and the second resilient compression element is configured to be placed adjacent a second side of the joist, thereby securing the spacer body to the joist. a spacer body defining a first fastener hole configured to receive a fastener having a longitudinal axis therein, the spacer body including a front surface, an opposing rear surface, a first side surface and a second side surface opposite the first side surface, the spacer body having a thickness extending from the front surface to the rear surface, the thickness intended to provide a preselected gap between a first board and a second adjacent board, a grip element joined with the spacer body, the grip element defining a second fastener hole aligned with the first fastener hole of the spacer body, the grip element extending forward and rearward of the spacer body and configured to fit in and engage a first groove defined by the first board, characterized in that: the spacer body includes a first resilient compression element extending outwardly from the first side surface of the spacer body and a second resilient compression element extending outwardly from the second side surface of the spacer body on opposite sides of a vertical axis of the spacer body, the vertical axis of the spacer body corresponding to the longitudinal axis of the fastener, wherein: the first and second resilient compression elements are configured to fit in the first groove and forcibly hold the spacer body in place adjacent the first groove during installation of the fastener; or the first resilient compression element is configured to be placed adjacent a first side of a joist and the second resilient compression element is configured to be placed adjacent a second side of the joist, thereby securing the spacer body to the joist. the spacer body includes a first resilient compression element extending outwardly from the first side surface of the spacer body and a second resilient compression element extending outwardly from the second side surface of the spacer body on opposite sides of a vertical axis of the spacer body, the vertical axis of the spacer body corresponding to the longitudinal axis of the fastener, wherein: the first and second resilient compression elements are configured to fit in the first groove and forcibly hold the spacer body in place adjacent the first groove during installation of the fastener; or the first resilient compression element is configured to be placed adjacent a first side of a joist and the second resilient compression element is configured to be placed adjacent a second side of the joist, thereby securing the spacer body to the joist. the first and second resilient compression elements are configured to fit in the first groove and forcibly hold the spacer body in place adjacent the first groove during installation of the fastener; or the first resilient compression element is configured to be placed adjacent a first side of a joist and the second resilient compression element is configured to be placed adjacent a second side of the joist, thereby securing the spacer body to the joist.