<p>A method of producing a plurality of effusion holes (22) in a wall (20) of a combustor (16) of a gas turbine engine (10) comprises: determining a hole pattern definition which provides a functional relationship of the spacing between each adjacent hole within the row of holes (22); using the hole pattern definition to identify individual positions of the effusion holes (22) to be produced; and using a hole producing system to produce the effusion holes (22) at the identified positions.</p>
