A hidden fastener assembly facilitates the attachment of grooved deck members to a joist. A body has an upper platform and a lower reference surface and is traversed by a central opening. A pair of tongues project from the body and are positioned and configured for reception in the grooves of the deck members. A pair of legs straddle the joist to aid in positioning. A fastener received in the opening and driven into the joist secures the deck members to the joist at a desired spacing. The fastener assemblies may be collated for usage in automatic driving tools.