Fei Gou (飛鈎)

Drawing of a Fei Gou, from 'Wu Bei Zhi (《武備志》)'.

Fei Gou (飛鈎, lit. 'Flying hook'), also known as Tie Chi Jiao (鐵䲭腳, lit. 'Iron sparrowhawk leg'), is a type of grappling hook used in siege defence. Unlike normal grappling hooks commonly used in naval warfare or to pull down obstacles, Fei Gou is designed to be used as a weapon. All four flukes on the hook are sharpened, and the front portion of the rope is replaced by an iron chain in order to prevent the enemy from cutting off the rope, as well as to prevent the sharpened hook from severing its own rope.

Fei Gou is used by siege defenders on top of a wall to hook at the vulnerable legs of besieging troops at the base of the wall (besieging troops near a wall usually keep their heads low to protect their faces from incoming arrows, so even a relatively large Fei Gou thrown from above can easily go unnoticed). Once a leg is caught, the defenders can pull the unfortunate victim to the top of the wall before releasing him and let him fall to his death. Furthermore, even if the victim manages to dislodge the hook before he is pulled up, he would still be taken out of the battle due to serious leg injury.