What is rug blocking?
When a rug is misshaped or has built-in wrinkles, sizing or rug blocking may help. A rug is resized by flipping it over, making it as square and flat as possible, and securing it along the edges. With their pile sides facing down, we apply natural starch to the backs of the rugs during the stretching and shaping process. Starch helps blocked rugs maintain their newly restored shapes after coming off the board. Note that even a good quality rug is rarely perfectly rectilinear. When blocking a rug the choice is sometimes between getting it flat or making it square--from the standpoint of what's good for the rug, it is almost always better to make the rug flat than to make it perfectly rectilinear.
Used with care sizing can make a rug more attractive and usable. Used incorrectly, blocking can distort or even damage a rug. Over-aggressive blocking will not remedy the problems of a poorly woven rug. Don't try this at home! Sizing or blocking is definitely a process best handled by an experienced rug repair person.