Hemorrhoids can occur either externally, outside the anal canal around the sphincter, or inside the anal canal. These are referred to as external hemorrhoids and internal hemorrhoids, respectively. Internal hemorrhoid size is classified by severity through a grading system. Hemorrhoids may be considered Grade 1, the least severe, up to Grade 4, the most severe. A Grade 1 internal hemorrhoid requires a tool to be used, such as an anoscope, to visualize the mass. A Grade 2 hemorrhoid is more extensive and will extend out of the anus during a strenuous activity like a bowel movement or certain physical exercise. However, a Grade 2 hemorrhoid will naturally return inside the anus after these activities have concluded. The same occurs with a Grade 3 Hemorrhoid; however, it will not return to its original position inside the anal canal and requires manual repositioning. A Grade 4 hemorrhoid is dangerous and very painful, as this hemorrhoid is so large that while its origin is within the canal, it extends outside of the sphincter. This does not occur with strain; instead, the hemorrhoid is always present outside the body and cannot be pushed back in. Typically, with a Grade 4 hemorrhoid, rectal prolapse also occurs, in which the lining of the rectum essentially falls out of the body with the hemorrhoid.