The saggital suture is the fibrous, tight, strong joint between the left and right parietal bones of the skull. It lies in the midline of the skull and runs in an anterior-posterior line.
The parietal bones of an infant's skull do not meet completely; the saggital suture consist of a broad, fibrous area called a fontanelle, or 'soft spot', on its anterior and posterior ends. The posterior fontanelle closes at approximately three months of age; the anterior fontanelle closes between seven and nineteen months of age as the bones move and grow toward each other.
The saggital suture remains fibrous until the skull has stopped growing, at which point the bones begin to fuse. This process starts in a person's twenties and continues throughout life.