The jiagun ( 夾棍) ankle crusher was a Chinese instrument of torture consisting of three wooden boards approximately a yard in length that were connected with cords, which when placed around a suspect's feet and gradually pulled, caused agonizing pain in order to force a confession.

The jiagun was a legal and non-lethal method for torturing men to confess, and for women there was the similar and less painful zanzhi finger crusher with small sticks and cords.

Several early European-language descriptions of China describe jiaogun (romanized as kiaquen) and zanzhi (erroneously teanzu) ankle and finger crushers, and were repeated in numerous later books up to the present day.

The torments on the hands is given with two sticks as big as two fingers, and a span long, turned round and full of holes in all places, wherein are put cords to pull in and out their fingers of both their hands are put into the cords, and little and little they do pinch them, till in the end they do break them at the joints, with an incredible pain unto them that do suffer it, and it causes them to give great shrieks and groans that will move any man to compassion.

And if it so come to passe that by this cruel torment they will not confess, and that the judge do understand by witness and by indiction that he is faulty and culpable, then doth he command to give him the torment of the feet, which is a great deal more cruel than that of the hands, and is in this sort: they take two pieces of wood, four square of four spans long and one span broad, and are joined together with a gume, and holes bored thorough, and put thorough them cords, and in the midst of these bords they do put the whole foot, and strain the cords, and with a mallet they do strike upon the cords, wherewith they do break all the bones, and cause them to suffer more pain and grief than with the torment of the hands.

Semedo had personal knowledge of the Chinese judicial system, he was "imprisoned for a year during the 1616 anti-Christian campaign and spent thirty days in a cage while being transported from Nanjing to Canton" (Brook 2008, 157).

For the feet they use an instrument called Kia Quen, it consisteth of three pieces of wood put in one Traverse, that in the middle is fixe, the other two are moveable, between these their feet are put, where they are squeezed and press, till the heele-bone run into the foot: for the hands they use also certain small pieces of wood between their fingers, they call them Tean Zu then they straiten them very hard, and seale them round about with paper and so they have them for some space of time.George Staunton's 1810 Fundamental Laws of China was the first foreign translation of the 1740–1805 Great Qing Legal Code, and gives precise instructions for constructing legal torture devices, including the jiagun and zanzhi.

This odd teanzu spelling exemplifies what linguists and lexicographers call a ghost word, an original typographic error that is repeatedly copied for generations.

The prolific author George Ryley Scott, who repeated the tean zu ghost word, describes brodequin torture, which was used in early modern Scotland and France: The prisoner was seated on a strong bench, and boards of suitable width and length were placed on the inside and outside of each leg, and tightly bound in position with strong rope, the two legs in their casing being fixed together.