I guess I should mention that my first photo is slightly smurfed. The grinding should happen on the side of the "T" that is going in the "valley" of the bit holder. The remaining "T" should be left untouched as that side engages nicely with the bit holder lock.
So in other words, you can choose the orientation of the teeth depending on which "T" you grind to fit.
Not only did I take a bad photo, I also (in my opinion) ground the wrong side!