What item should be placed between any wall and the butt end of a power stretcher?

The item that should be placed between any wall and the butt end of a power stretcher is a stretcher board. This board serves as a protective barrier that prevents damage to both the wall and the stretching tool itself. Specifically, the stretcher board helps distribute pressure evenly across the surface during the stretching process, maintaining wall integrity and ensuring that the power stretcher functions effectively without causing harm.

Using a stretcher board properly also aids in the installation process by ensuring a clean and precise stretch of the carpet, which is essential for achieving a professional finish. Other items, such as a padded rug, knee kicker, or transition strip, do not serve the same protective or functional purpose in the context of using a power stretcher. A padded rug would not provide the necessary rigidity and support; a knee kicker is a manually operated tool for stretching smaller areas; and a transition strip is used for joining two different types of flooring rather than for protecting walls during carpet installation. Thus, the stretcher board is the correct choice for this specific scenario.