an area of a garment more rigid. interfacings can be used to: [ ] stiffen or add body to fabric, such as the interfacing used in shirt collars strengthen a certain area of the fabric, for instance where buttonholes will be sewn keep fabrics from stretching out of shape, particularly knit fabrics interfacings...
can be cut from fabric in any orientation, and the chosen grain or orientation will affect the way the fabric hangs and stretches and thus the fit of a garment. generally speaking a piece is said to be cut on a particular grain when the longest part of the pattern or the main seams of the finished piece...