Default Shortcut: None
Menu Path: Subdivision > Crease Edges
The Crease Edges command allows you to change the way an object is subdivided. Creasing an edge lessens the smoothing effect of the subdivision algorithm for that edge, resulting in a creased or hardened line on the subdivided object.
In terms of the subdivision algorithm, a crease causes the vertices of that edge to be less displaced, i.e. less smoothed, than they would otherwise be. Creased edges have a cumulative effect on the vertices they share, so a vertex with three or more attached edges creased will be in the same place on the subdivided shape as it was on the control mesh, while a vertex with none of its edges creased will be smoothed normally. Experiment with this command to learn how to use it effectively.