A system and method for movably sealing a vapor deposition source is described. One embodiment includes a system for coating a substrate, the system comprising a deposition chamber; a vapor pocket located within the deposition chamber; and an at least one movable seal, wherein the at least one movable seal is configured to form a first seal with a first portion of a substrate, and wherein the first seal is configured to prevent a vapor from leaking past the first portion of the substrate out of the vapor pocket. In some embodiments, the movable seal may comprise a first flange, wherein the first flange forms a wall of the vapor pocket; and a second flange, wherein the second flange is configured to be movably disposed within a first groove of the source block.