How to make internal angles with wallpaper
To make the inner angle neatly, it is better to connect two canvases, especially if there is no clear verticality of the wall.
First, we measure the necessary width of the canvas to the corner. To do this accurately, taking into account the possible irregularity of the wall, we do it at three points. Add 15-20 mm to the required width for the junction. Then, using a plumb line, determine the position of the second canvas. And glue the canvas, closing the left reserve of the previous canvas. Gluing angles does not start from the corner, but from the marked vertical. The thicker the wallpaper, the less you need to make a margin for overwhelming.