When planets in three different signs of the same modality (cardinal, mutable, or fixed) form an opposition (a 180-degree aspect) and a square (a 90-degree aspect), this is called a T-Square aspect.
Two of these planets are in opposition to each other, and the third planet makes a square with them. One of the four signs in the mode will not touch any of the planets in the T-Square.
Both squares and oppositions are hard for the native because the conflicting energy makes the energy stiff and hard to move. When this opposite energy comes together, the results can be very strong.
T-Squares can be dangerous or explosive because there is a piece of the puzzle missing: the planet in the fourth sign of the same mode that isn't there, which means the house is empty.
The Cardinal T-Square will give the natives the confidence to go after what they want. Cardinal signs like Aries, Cancer, Libra, and Capricorn are all about starting new things and giving it their all to finish what they start.
With a Fixed T-Square, the native will be too focused on keeping the same habits and not changing them. They may also be stuck in the past and unwilling to move on. Taurus, Leo, Scorpio, and Aquarius, all of which are fixed signs, have planets in this square.
People with a Mutable T-Square will have three of the Mutable signs Gemini, Virgo, Sagittarius, or Pisces. If there are no planets in the sign of Virgo, they might not have the drive they need to fully commit to a cause. By giving them a sense of structure, they will be able to make their dreams come true.