When we say “canvas,” we’re not talking about the stuff your duffel bag is made of, or a politician glad-handing for votes. We’re talking about the layer that sits between the outer cloth and inner lining of a suit jacket or blazer and gives the garment structure. It’s generally comprised of wool and horsehair, the latter of which is stiff enough to give the jacket some shape. Sometimes cotton or rayon enters the mix to soften things up a bit, and some tailors use camel hair instead of horse. A “full canvas” spans the entire jacket from collar to hem, and a “half canvas” covers the top half only.
The alternative to this old-school approach is “fused” construction, where a glue-like synthetic is applied to the outer cloth to make it more rigid. Canvas, on the other hand, “floats” between the inner and outer layers of the jacket, moving more freely along with the wearer. It also conforms to the wearer’s body over time, and purists contend that it breathes and holds up to dry cleaning better than fused options. It also takes quite a bit more work than fusing, due to the manual labor involved, but if you’re buying a suit for the long haul (and really, why else buy a suit?), it’s well worth it.