← Encyclopedia of Astrology · lesson 159/235
T-square
The shape
A T-square takes three planets. Two of them face each other across the chart in an opposition, and the third sits roughly halfway between them, in a square to both. Drawn on the wheel it looks like a capital T, or a right-angled triangle whose long side runs straight across the circle.
A worked example: the Moon at 10° Aries opposes Saturn at 12° Libra, and Mars at 11° Cancer squares both. Each leg has to be a genuine aspect within its orb, and the figure is only as tight as its loosest leg — here every contact is within two degrees, so this is a close one.
What it is made of
Three aspects and nothing else: one opposition and two squares, all of them hard. That is why the T-square is read as a figure of friction and drive rather than ease. It is also a part of a larger shape: add a fourth planet opposite the apex and the T-square becomes a Grand Cross, which holds four T-squares at once.
The apex
The square-making planet is the apex, or focal planet. The opposition is a tug between two ends; the apex is where that tug comes out as action. In the example, Mars in Cancer is the planet that has to do something about the argument between the Aries Moon and Libra Saturn — and it may tend to overdo it.
The point opposite the apex is called the empty leg (here 11° Capricorn). Nothing sits there, and the tradition reads it as the quality the figure is missing: the place a person can learn to stand in so that the pressure has somewhere calmer to go. Transits across the empty leg often bring the pattern to the surface.
By mode
Because the three planets usually fall in signs of one mode, the mode colours the figure:
- Cardinal — the quickest to act and the most crisis-prone, inclined to plunge in before weighing things.
- Fixed — concentrated power that builds and then breaks out; great staying power, which wants a constructive outlet.
- Mutable — adaptable to a fault, easily pulled about; it asks for a clearer sense of purpose.
In a chart
A natal T-square is common, and it is one of the strongest motors in a chart. It tends to show where someone feels pushed, and where they push back hard enough to achieve something. The houses involved say which parts of life are pulled into the argument.
In the sky
The same figure can form in the passing sky, or between a transiting planet and a natal square: a transit that turns a lifelong square into a T-square for a few weeks is a dated event, with a beginning and an end, rather than a description of character.