Gap standardization technique for specialized fillers

A system is provided for filling a gap between adjoining coplanar first and second sheet members mounted on an outer surface of a common substrate and having juxtaposed first and second edge surfaces. A permanent gap filler member of predetermined shape and size intended for eventual permanent reception in the gap is employed for partially filling the gap. A temporary gap filler tool which includes a substitute gap filler element having substantially the same predetermined size and shape of the permanent gap filler member, has an abutting surface for contiguous engagement with the first edge surface of the first sheet member when advanced to an attached position before the permanent gap filler member is mounted in the gap, a minor gap surface facing opposite said abutting surface, and means for releasably attaching the temporary gap filler tool to the first sheet member. A minor gap is thereby defined between the temporary gap filler element and the second edge surface of the second sheet member. Fairing material is initially laid down as an epoxy resin slurry in a minor gap resulting between the substitute gap filler element and the second edge surface of the second sheet member, then cured to hardened form having a substitute second edge surface contiguous with the minor gap surface of the substitute gap filler element. Thereafter, the temporary gap filler is removed from the gap and the permanent gap filler member is inserted and bonded to the common substrate resulting in the entire gap being filled.