Fatback by John Spottiswood.

This is a slab of fat that runs along the back of a pig. You can render it into lard, cut it into barding strips to wrap around lean roasts, or use it to line terrine or pâté pans. It you're cutting it into sheets, it helps to put it in the freezer first until it's firm. It's also sometimes cured like bacon. It's hard to find, ask your butcher.