In most residential construction, window openings are already framed out with wood in order to use nails or screws to attach the window in place. If an adjustment to the opening is needed, keep it as close to the window size as possible. Allow about a 1/4 inch gap on all the sizes for adjusting. With log homes, the logs tend to settle or shrink over the years. Therefore a window jamb or a frame must be installed that won't shrink. Slides connect the sides of the frame to the log. In this way, the logs are able to move and shrink as they age without disturbing the window.