Arm Movement inside a slot
[vidwrap type=qq file=https://v.qq.com/x/page/u324332h3pz.html ]
The hand, elbow and shoulder must form an open-triangle shape and then put this open triangle inside something like the open slot between the two panes of a double-pane glass window. There are the restrictions for the arm.
Now you can moves your arm according to the rules of Chen Style taijiquan practical method.
The video clip is from an online Level 5 instructor's private class. Sorry the original video is for people of that group only. 夹在平面-5级教练花絮20210430
Source: https://practicalmethod.com/?p=75350