at the same time provides resistance against their arm from simply folding and taking your teeth out.
There are lots of examples of a bracing angle in Kenpo. The most prominent one that stood out to me when I was learning these techs so long ago was Flashing Wings for reason. It clicked. You have to pivot into them when you deliver the right outward elbow. If you don't, your elbow has nothing on it and you will simply fall over.
A bracing angle check is just a check that creates a bracing angle.
Hope this helps,