Solunars by Aldebaran Sidereal Academy

That is to say the planets , make aspects to the angles ?

If for example Saturn in transit squares natal IC, would you expect problems, troubles related to the home, for example?

The simple answer to exactly what you asked is, yes, squares to angles (within tight orbs) are valid, although CALLING them "squares to the angles" is misleading because:

1. Angles don't make or receive aspects (any type of aspect besides conjunction)
2. The ecliptical squares to angles are actually other angles - squares to Asc being the longitudes of Zenith and Nadir points, and squares to MC being the longitudes of Eastpoint and Westpoint.

We used to more commonly call these "squares to the angles," but a while back I realized this was misleading people into thinking angles made aspects (and causing questions like, "If they make squares, then why not trines?"). I documented and explained the change of language here: viewtopic.php?f=15&t=4659

Regarding your second question about interpretation: How much individual angles can be distinguished interpretively is an ongoing debate and exploration. At the very least, the pure fact of a planet being angular - ANY angle - is vastly more important than which angle is involved, to the point that one can ignore the specific angle and rarely (ever?) miss anything. So much that seems evident from a planet being on a specific angle already is part of what we expect from the planet being angular at all. To use your example, Saturn on any angle is known to indicate that the original home environment, parent relationships, and life conditions were harder than average - I just wrote about Alan Arkin's chart with Saturn exactly rising and his impoverished upbringing to the point of going without food and, sometimes, without shelter. If he had Saturn exactly on IC, we might have said, "Wow, what a clear sign of his early hardship," but it's just as clear with Saturn on Ascendant.

To the extent that individual angle meanings can be distinguished (and the distinction is so proportionately weak that I'd be willing to accept that it is a fiction), it does seem that the meaning follows the direction of the angle rather than what it ecliptically squares. That is, the upper and lower squares to Ascendant do not take after Ascendant but are more themed to 10th House (Zenith) and 4th House (Nadir) ideas, while the east and west squares to Midheaven do not take after MC-IC but are more themed to 1st House (Eastpoint) and 7th House (Westpoint) ideas.

Thank you Jim