Jin Gang Dao Dui is one of the signature techniques of Chen-style Taijiquan. Yet its martial application is not widely understood.
I believe this may be partly because its application has traditionally been taught within limited circles, and because the meanings behind the movements may not have been fully passed on when transmission focused primarily on the form.
For a long time, I hesitated to share this application publicly. However, I have come to believe that explaining the meaning behind the movements of the form is also part of my responsibility as someone who carries on the tradition of Chen-style Taijiquan.
In the application passed down to me, the name Jin Gang Dao Dui describes the technique itself. Dui（碓）refers to a tool for pounding grain, while dao dui（搗碓）describes the action of pounding grain in a mortar with a pestle. Jin gang（金剛）evokes an image of unshakable strength.
As shown in the photograph, the application involves holding the opponent’s head against the right knee and bringing the right fist down toward the head.
Looking at the corresponding movements in the form,
the right knee represents the mortar, the left palm represents the grain—the opponent’s head—and the right fist represents the pestle in a hammering motion.
This application requires more than strength alone. It involves maintaining a connection with the opponent and responding to their movement without meeting their force head-on. Here we see the Taijiquan principles of chan si jin（纏絲勁, silk-reeling power）and hua jin（化勁, neutralizing force）at work.
Positioning the opponent’s head against the knee involves two movements. In the video, please observe how I move while maintaining a connection with my partner, and compare this with the corresponding movements in the form.
For safety, the strike is deliberately directed away from my partner during the application demonstration.
I hope this comparison helps you appreciate that every movement in the form has meaning, and that these movements reflect the underlying body mechanics of Taijiquan.
Watch Jin Gang Dao Dui: Application and Form (20 seconds)