1. Combining materials Interfacings Underlining Linings Interlining
Types and applications in relation to weight, construction, use

4. Combining materials Interfacings
There are so many types: fusible and non-fusible; wovens, non-wovens and knits different weights, colors and brands. How are we to decide which one to use with all these factors? The task of selecting interfacing can be simplified when you understand why we use it and some of its characteristics. 
Interfacing is it a third layer of fabric applied between two other layers to provide shape, stability and structure to garments and to enhance durability.
It is used in buttonhole areas to keep them from stretching and distortion, in collars and cuffs to add crispness and in facings to give stability.
In tailoring, it allows the garment to retain the shape that is built in during the construction process.
It can be used for special dramatic effects in costuming. In order to understand interfacing, it is important to look at some of the differences.

5. Interfacings cont’d
One of the major characteristics is in the structure of the
fibre. 
Woven interfacings are stable. They offer firm support and are available in many weights. 
Knit interfacings are drapeable and soft. They are generally light weight. 
Non-woven interfacings are made of synthetic fibres. They are neither woven nor knit
Non-fusibles (also referred to as “sew-ins”) may be softer and less likely to change the hand of the fabric

6. Underlining
Underlining differs from lining in that the underlining is included in the seams while a lining is made separately and used to hide the seams.
Underlining reduces wrinkling and can make a fabric that would be considered too wimpy for a skirt or jacket substantial enough so that the completed garment has enough body.
Adding an underlining can supplement or change the weight, hand, or drape of a garment fabric. Duplicate the pattern piece that needs help in a second fabric, and work with the fashion fabric and underlining as one.
Underline, for example, to support a limp fabric with a firm fabric, or a loosely woven fabric with an opaque one.
Always treat the underlining fabric as the secondary fabric; don't let it outweigh or dominate the primary fabric.

7. Lining
Lining serves the purpose of increasing the quality and value of a garment by improving both its appearance and performance.
Lining improves the hanging properties of the outer cloth and also protects it from perspiration, rubbing and staining.
A garment's shape is maintained to a higher degree if lining is present.
A lined garment is also easier to put on and take off as well as being warmer.
Lining also hides seams and stitches and makes thinner fabrics less see through.

8. Linings
The presence of lining on a garment also allows the construction of details such as outer and inner pockets, the covering of lapels, finishing of waistbands and back panels of waistcoats.
Linings should have the following requirements:
Comfortable wearing properties
Tolerance to being used
Drying and washing conditions.
These requirements can be met by the correct choice of fibre type, fabric structure, density and finishing.
The most common materials used to make linings are filament yarns of viscose, polyester, acetate, nylon, cupro or silk.

9. Interlining
The major function of interlining is to maintain the shape of a garment.
A large number of interlining materials are currently available which satisfy a highly diverse range of requirements including elasticity, padding, stiffening, formability and tolerance to many different manufacturing, end use, and aftercare processes.
They may be constructed from a wide range of fabrics and supplied either for fusing or for sewing
Gore-tex membrane is a branded interlining used as the “filling” in a main fabric and lining fabric “sandwich”
Wadding would be an interlining used to add insulation properties to an item of clothing or even curtains. Wadding is also used in quilting to add a decorative effect

10. Embroidery Backings
There is quite a number of reasons, why you should not miss an embroidery backing:
achieves clean outlines of the motif
provides stability to fabrics 
Reduces friction during the stitching process
All in all: embroidery backings improve the quality and secure an efficient production.