A computer-implemented method is disclosed. The method comprises receiving object data relating to a three-dimensional object generated or to be generated using an additive manufacturing apparatus, the object data including details of an aperture in a surface of the three-dimensional object; determining, based on the object data, design data for a jig to engage the object and to form a fluid communication channel between the aperture in the surface of the three-dimensional object and an interface of an airflow control mechanism, the airflow control mechanism to cause a flow of air through the aperture; and providing the design data for delivery to an additive manufacturing apparatus to generate the jig. A jig is also disclosed.