In 2015 I stayed one month at the Daqinshan Practical Method training centre of Master Chen’s. One evening training session Master Chen was explaining one of the facets of the importance of the Chen Style Tall Hand Posture during all your exercises (yilu, push hands and foundations unless stated otherwise). This account is my subjective view on what he explained and invite everyone to add their thoughts or to correct me, please.
He came around to test every student’s power of the stretched hand:
You have to have a straight hand by stretching your fingers, a locked wrist that is not bending like it has been welded and a stretch from the middle finger needs to go straight all the way to the point of your elbow and other way around at the same time. The idea is that the stretched lines from your fingers extend out of your fingers in an unlimited long line vertically up.
Keep your forearm vertical with fingers up and elbow down in front of your body.
Use your other arms stretched hand and beat upon your fingers of the vertical underarm.
Master Chen explained that your stretched hand should be strong enough to withstand your beatings by the other hand when you test yourself. He then came to test everyone and explained that you can repeat this way of testing (by yourself and each other at your own schools). Of course, watch out you do not hurt yourself or others, fingers should not be injured. Master Chen beat my upward stretched fingers and told me my stretched hand feels powerful and explained that I have Buddha’s Fingers.