The inside of construction of a jacket concerns the front, the shoulder and the upper sleeve. Depending on the style of the suit, the shoulder and sleeve header shall be considered a priority.
The front part of the jacket is reinforced in order to ensure a net fell, free of pleats and folds. Furthermore, these reinforcements, guarantee the durability of the jacket.
In all those cases, the higher part of the front-piece at the shoulders level is more reinforced to create a development for the chest. This part made of natural wear the jacket, the canvas conforms to the body shape, allowing the suit keeping it from sagging or deforming, much like the foundation of a house.
When creating a Full Canvas jacket, the canvas made of natural fiber is being cut to the jacket's shape, then the wool is manually stitched to the canvas. As you wear the jacket, the canvas conforms to the body shape, allowing the suit fabric to drape naturally, giving a clean well put together look. Nowadays, only a few luxury brands offer Full Canvas garments because they involve a lot of time and manual work.
The Half Canvas method, as it's name suggest, it's the halfway between full canvas and fused chest piece method. Just like the full canvas method, the lapel is stitched, but the front piece remains largely fused. Half-canvassed jackets have several benefits. They generally have a lower price than a similar fully canvassed jacket, they drape naturally across the chest, also being long-lasting.
The Fused method has the advantage to be easier and also much cheaper. As the name suggests, fused garments have almost all reinforcements assembled by gluing. Nowadays, fusing technology has improved to the point where you may never experience bubbling or other problems. But a full-canvas jacket will always have that natural elasticity and will last longer giving you the pleasure of wearing high-end apparel.