Interfacing is essentially an extra layer of fabric that provides shape and support in detail areas. And is commonly used in collars, cuffs, lapels, necklines, pockets, waistbands, buttonholes, facings and opening edges. Interfacing acts to keep these areas of your garment crisp through repeated washings and wearings Bondaweb is an extra strong, heat reactive, adhesive web which permanently bonds one fabric to another when ironed.