Sizing a wall refers to a coat of paste you apply to the wall prior to wallpapering. This process creates a uniform surface for the wallpaper to adhere. Although sizing is not always necessary, it has many benefits including easier wallpaper application, increased grip between the wallpaper and the wall, and easier wallpaper removal. It is especially recommended for wallpapering on plastered, repaired, or porous walls. Once your walls are clean and smooth you are ready to begin sizing.