A method of correcting for pattern run out in a desired pattern in directional deposition or etching comprising the steps of providing a test substrate; providing a stencil of known thickness on the test substrate; providing a stencil pattern extending through the stencil to the test substrate. exposing the test substrate through the stencil to a source of directional deposition or etching; comparing the stencil pattern to the pattern on the substrate at a plurality of points along at least one direction to determine pattern run out at said points; fitting the measured pattern run out as a function of position to a function of the form ΔX=MX+C where ΔX=pattern run out, X=position on the substrate, M=Magnification and C=translational offset; providing a further substrate at a known position relative to the first; providing a further stencil of known thickness; adjusting the magnification to allow for the difference in stencil thickness between the test stencil and the further stencil; adjusting the transitional offset to allow for the difference in position of the test substrate and further substrate along said direction; providing a desired pattern to be deposited or etched on the further substrate; correcting each point of the desired pattern by the inverse of the determined pattern run out at the point; providing the corrected desired pattern on this further stencil, the pattern extending through the further stencil to the substrate; exposing the further substrate through the further stencil to the directional source of deposition or etching.