Abstract: A method and apparatus for forming an opening in a concrete wall is provided. More specifically, interlocking concrete forms comprising parallel spaced insulation panels are provided for receipt of concrete. Any openings, i.e. such as for windows and doors, are accommodated within the insulated concrete forms by way of a customizable buck. The buck members utilize less material than those of the prior art, and are easily customized to yield a required opening size. The placement of concrete into the form yields a concrete wall with the desired window or door opening.