Sometimes regular wallpaper paste is not sufficient to hold down the edges of the wallpaper. Wallpaper sometimes gaps at the edges if most of the paste is squeezed out when the seams are rolled or the paper is soaked too long and the paste runs off the edges. Special wallpaper seam adhesive is stronger than regular wallpaper paste and is designed to hold down these loose edges.
Dip a small artist's paintbrush in the wallpaper seam adhesive, which is available at hardware stores. Apply the paste to the back of the loose paper. Try not to fold the paper back as you apply the paste.
Smooth the paper in place and use a wallpaper seam roller to firmly press the seam down. A seam roller is a small wide wheel with a handle, it looks like a tiny, short paint roller. Roll the wheel along the seam, pressing firmly. Start rolling above the glued area and continue rolling several inches below the glued area.
Overlap the printed side of any torn paper over the side with the white edge. If there is a tear in the edge of the paper, glue the side of the tear with a white edge down first. Place the side that has colour all the way to the edge over it. This will keep the tear from showing.
Try to fold the wallpaper back as little as possible when you apply the paste.
Follow all manufacturer's directions when using the adhesive.