Cutting the surface of your dough with a razor or sharp knife just before baking, giving the bread a controlled place to expand.
Without scoring, your bread will crack open wherever the crust is weakest -- usually at the seam, and usually ugly. A deliberate score directs the oven spring, creating a clean opening. Score at a 45-degree angle for an ear; score straight down for a more open split. The surface should be slightly dry for clean cuts. Cold-retarded dough scores much more easily than room-temperature dough. Decorative scoring (wheat stalks, leaf patterns, geometric designs) is optional and purely aesthetic.