away from the archer when the bow is unstrung. The cross-section of the limb also varies; the classic longbow is a tall bow with narrow limbs that are D-shaped in cross section, and the flatbow has flat wide limbs that are approximately rectangular in cross-section. Cable-backed bows use cords as the back of the bow; the draw weight of the bow can be adjusted by changing the tension of the cable. They were widespread among Inuit who lacked easy access to good bow wood. One variety of cable-backed bow is the Penobscot bow or Wabenaki bow, invented by Frank Loring (Chief Big Thunder) about 1900. It consists of a small bow attached by cables on the back of a larger main bow. In different cultures, the arrows are released from either the left or right side of the bow, and this affects the hand grip and position of the bow. In Arab archery, Turkish archery and Kyūdō, the arrows are released from the right hand side of the bow, and this affects construction of the bow. In western archery, the arrow is usually released from the left hand side of the bow for a right-handed archer. Compound bows are designed to reduce the force required to hold the string at full draw, hence allowing the archer more time to aim with less muscular stress. Most compound designs use cams or elliptical wheels on the ends of the limbs to achieve this. A typical let-off is anywhere from 65% to 80%. For example, a bow with 80% let-off only requires to hold at full draw. Up to 99% let-off is possible. The compound bow was invented by Holless Wilbur Allen in the 1960s (a US patent was filed in 1966 and granted in 1969) and it has become the most widely used type of bow for all forms of archery in North America. Mechanically drawn bows typically have a stock or other mounting, such as the crossbow. Crossbows typically have shorter draw lengths compared to compound bows. Because of this, heavier draw weights are required to achieve the same energy transfer to the arrow. These mechanically drawn bows also have devices to hold the tension when the bow is fully drawn. They are not limited by the strength of a single archer and larger varieties have been used as siege engines. Types of arrows and fletchings The most common form of