•     The two layers are permanently joined and will not slip or slide.
•     Speeds up construction because it eliminates a sewing step

Disadvantages of fusible interfacing

•     The act of fusing can shrink the fabric and interfacing so it does not quite match the original size.
•     The bond does not always hold and bubbles on the surface of the fused fabric may appear after washing.
•     Cannot be used with heat sensitive fabrics

Structure: Woven, Knit, Non-Woven and Weft Insertion

Woven interfacing made from woven fabric. Woven interfacing may be fusible or non-fusible. It may be lightweight, heavy or any weight in between.

You can tell by looking at it whether an interfacing is woven. You will see the warp and weft threads and it will look like woven fabric. In fact, you can use various stiff or crisp woven fabrics such as organza or organdy as interfacing.

Woven fusible interfacing is usually relatively light weight. One side may appear to be shiny. That is the adhesive. Alternatively, you may see tiny dots of adhesive.
Lightweight woven interfacings are good for use in cuffs and facings of light to medium weight blouses, and dresses, but may also be used in quilting and crafts.

I use lightweight woven fusible interfacing to back fabrics for beading, or to block shadows in applique. When appliqueing with light colored fabric over darker fabrics, the darker fabric can show through the lighter one. To prevent this, the lighter colored fabric can be interfaced.

Heavier woven interfacings are used for tailoring. The most common interfacing for tailoring is hair canvas which at one time was woven from goat hair.

Knit interfacing will appear to be knit. You will see threads in a knit configuration. The interfacing will be soft, not stiff. Once again you will see some sign of the adhesive on one side. Brand names include Easy-Knit or Fusi-Knit. You may see the word "tricot" on the bolt. Knit interfacing has stretch, so is the ideal choice for use with knit fabric. It can also be used on woven fabric, when you want a softer feel than might be obtained by using woven interfacing.  

Non-woven types are perhaps the most common interfacings. I am not too fond of them because they tend to pill and disintegrate over time. Their structure is felted, in other words you will not see warp or weft threads or knit threads, but pressed fibers that look a bit random. These products are not held together by woven or knitted threads, but with adhesives that disintegrate over time and with multiple washings. You may use non-woven interfacing in a pinch, but I do not use them for fine garment making.

Weft-insertion is a type of interfacing that is mostly used in tailoring. It is usually medium heavy weight. It is a knit interfacing that is stabilized with a weft thread inserted into the knitted rows. The knit structure makes the interfacing pliable, while the weft thread provides stability. So although the interfacing is knit, it is also stable and does not stretch.  Weft insertion is a specialty interfacing, not for common use but a good choice for machine tailoring. Brand names include “Armo-weft” or “Whisper weft”, a lighter weight version.

There are a plethora of craft interfacings made for special purposes and interior design. Some of the heaviest types include Timtex and Fast2Fuse. These two products are used for very stiff crafts such as notebook covers, stand-up houses, fabric bowls and vases. Fast2 Fuse is the fusible version. Timtex is not fusible. Be aware that these heavy interfacings crease easily and usually permanently. 

Stabilizer

Fusible Web