It is used to roughen surfaces of hard wood which are to be glued together, for otherwise the glue would not adhere well.

Some tropical woods are so hard that their surfaces can be reduced only by a scratch-plane.

It is also useful in preparing the surface of a very cross-grained piece of wood which cannot be planed without chipping.

By first scratching it carefully in all directions, it can then be scraped smooth.

It is also called a _scraper-plane_, because accompanying the plane is a scraper which can be inserted in the same stock and inclined at any required angle.