Trimming knives are an ideal way to create a long smooth cut in paper that follows the contours of a corner or skirting board.
Trimming knives are also the only way to double cut wallpaper
They differ from normal utiliy knives in that the blade is long and made of upto 10 segments. As the tip becomes blunt so a segment can be snapped off with pliers or an included special tool to expose the next new and sharp blade.
The blades are much finer than typical utility blades which enables double cuts to be imvisible when done properly.
It is important to regularly snap off a blade. Blunt blades will cause the paper to tear rather than cut.