Bodkins were a popular type of arrowhead in Western Europe during the Middle Ages. The basic shape was a squared off head, terminating in a point. Edges were generally not sharpened.
Actual geometries to the Bodkin vary widely.
There is some debate as to whether or not Bodkins were designed to penetrate armor. They probably weren’t designed at first as penetrators, but rather, it is simple design easily mass produced, using less metal than broadhead style arrowheads. The shape however, would help to penetrate mail, leather, and cloth armor. The question is whether or not it was effective against steel plate armor.
Fueling the argument is a claim that Bodkins were not made of hardened steel, something that would make them much less effective against plate armor. However, the number of Bodkins tested is quite low, so we can’t really say for sure.
But, looking at historical sources, it seems that hardened tips were unusual, at least until the Mongol invasions. A manuscript by Friar John of Plano Caprini details how the Tartars (a term used for Mongols) dip their arrowheads “red-hot into salt water.” Some may recognize this as a hardening technique. From the way that Caprini phrases it, I surmise that hardened steel and it’s associated metalworking techniques were not applied to arrowhead manufacturing in Europe before the 12th Century.
It’s likely that after the Mongol Invasions, the practice spread. Hardened Bodkins combined with the incredible power of Yew Longbows most likely ensured the longbow’s use by the English well into the 15th Century.