The Wedge aspect pattern consists of two planets in opposition, with a third planet in trine aspect to one and sextile to the other. The third planet is the apex planet and forms a triangle shape with the two opposition planets.
The opposition creates stress or conflict of some kind. The apex planet provides an outlet or release or extra dimension with the other two planets. For example, in the case of a T-square, the apex planet squares the other 2 planets that are in opposition. In the Wedge aspect pattern, there are two planets in opposition and the apex planet is sextile to one and trine to the other. In the Yod, the apex planet disrupts and challenges the cooperation of the two sextile planets.
In Huber astrology, this figure is called an Ambivalence Triangle.