A crossbow is a weapon that consists of a prod (similar in appearance to a bow) mounted on a stock similar to a rifle stock, which has a mechanism to wind and shoot its bolts. These bolts are typically called quarrels, and do not depend upon lift as arrows do. Crossbow bolts must be made to have consistent weights as the mechanical process of engaging a bolt forces a more uniform process than that of using a bow and arrow. It is this consistent performance which has made the crossbow historically a significant force in warfare.
A crossbow contains a string which is held in place by a nut when the bolt is loaded and the cross bow is engaged (referred to as at full cock). Typically, the nut is at the end of the shelf (also called the bolt rest).
The prod ("bow") and stock of a crossbow were made of good hardwood, such as oak or hard maple. The central European bows were rather exotic as they were constructed of inlays as well as specialized woods. The prod is attached to the stock with hemp rope, linen, whipcord, or other strong cording. This cording is called the \'bridle' of the crossbow. Much as a horse's bridle, it tends to loosen over time, and must be carefully respliced when appropriate.
The crossbow shelf is a flat section above the stock with a straight groove for the bolt to rest upon and travel along as it is shot.
The strings for a crossbow are typically made of strong fibers that would not tend to fray. According to W. F. Patternson, whipcord was very common; however linen, hemp, and sinew were used as well. Even cotton was tried with some success.
The crossbow also includes a trigger, which was later incorporated into rifles, muskets and other firearms. Triggers are known to have been used on crossbows from the early 1400s. Leonardo da Vinci designed many complicated triggers for crossbows, ultimately producing a "hair trigger" that could be shot with very little finger strength.
Crossbow bolts are lighter than arrows, but must be sealed with a varnish to ensure their consistent weight. They also typically only have two fletches per bolt instead of three commonly seen on arrows. This allows them to not snag on the crossbow nut as they are shot.
An Iolo is a variant form of a crossbow.
The history of the crossbow is varied. In China in the 200s B.C., the crossbow (nu, 弩) was well developed, including a lock mechanism that was self resetting. Roman bows tended to be ornate and well engineered, yet western European bowstocks that were produced 600 years later appeared to be nothing more than rough hewn slabs of wood. Crossbows were actively being used from 800 to 1500 A.D. About 1400 the use of the crossbow changed, with the butt end of the stock being placed on the shoulder for accuracy. By 1650, the cross bow looked like it had a rifle stock, and was used in a similar way. Makers of cross bows (also called arbalistmeisters) were making quite beautiful crossbow stocks by 1600. Some Belgian designs were as polished as those of modern Olympic rifles.
The prod of a crossbow was made of wood or composite materials until the middle of the 15th century.The advantage of a simple wooden prod is that the bow as a whole was lighter in weight. Composite prods were made of horn, sinew and wood, and produced much larger draw weights. The draw weight is the tension that the string is under when the bow is engaged. Since the draw weight can be much more than a soldier might be able to pull, these crossbows generally include a winch device to cock them. It is the high draw weight (or poundage of a crossbow), which made the crossbow a formidable weapon in warfare. Since composite prods involved gluing material together which would have to withstand a great deal of stress, a slow drying time was essential. The strongest glues naturally took longer to dry. It was not uncommon for six months up to a year to be spent in ensuring a bow was dried properly. In the later 1400s, steel manufacturing advanced significantly, and was more commonly used in spring production. A crossbow prod is actually a specialized form of a spring, although not a coiled spring. Steel prods became very common by the early 1500s as their performance was more uniform, except in very cold weather.
Person loading a winching crossbow.
Modern crossbows are still used for target shooting and in some places for hunting. They are made of the same composite materials as modern bows.
See also: arbalest, Crossbow (video game)