A technique is described to generate an optimum set of points beyond the boundary of a finite-difference model; points which can be used for finite-difference operations, and which eliminate reflections from that boundary. The rationale is explained, the mathematics are developed, and the final formulae are given. Examples are shown for the case of a two-dimensional elastic pressure wave. The limitations of the technique are shown to be consistent with the general limitations of simulating continuous waves by finite-difference techniques.