Brims on a sugarloaf hat are turned up or down, but do not project approximately perpendicular to the head, even to eventually curve upward or downward. A blocked felt smooth crown shape. The head opening may be flat and continuous, or may be cut to better fit over the forehead and ears. It if often constructed of four roughly truncated lozenge-shaped pieces of blocked out of felt. Some bonnets are knitted.
Some bonnets have a pronounced ridge or two ridges running perpendicularly on the crown.
Accept as bonnets all hats that have pronounced ridges whether the crowns are square or rounded. The crown generally widens from the head opening towards the top of the crown. The silhouette is usually pentagonal, but sometimes may be trapezoidal with a narrow base and broader top. Usually brimmed, but the brim may be continuous or partial, tall or short relative to the crown height. Brim heights may vary from very narrow to so high that the crown cannot be seen.