A fingerprint can be grouped into one of eight sub-pattern types: plain arch, tented arch, ulnar loop, radial loop, plain whorl, double loop whorl, central pocket loop whorl, or accidental. Because a loop fingerprint cannot readily be distinguished as flowing out the ulnar or radial side of the hand, loops are often referred to as right loops (right-slanted loops) or left loops (left-slanted loops). Loops are the most common fingerprint patterns in the population. Approximately 60 to 70 percent of fingerprints in the population are loops. Loops are patterns in which the ridges enter on one side of the finger, make a U-turn around a core, and exit out the same side of the finger. Loops are further characterized by their ridge count. Ridge count refers to the number of friction ridges that cross an imaginary line between the core and delta.