A few personal considerations on the yod...

The Yod is a rare astrological aspect that involves any three planets or points in the chart that form an isosceles triangle, and Yods can be formed within several Harmonics, such as the Biquintile Yod or the Quindecile Yod, but these thoughts are about the 6th/12th Harmonic geometrical structure, the classic Yod formed by two Quincunxes connected through a Sextile.

• All Yods are Boomerangs; I'm not sure the term Boomerang is the best term for this structure, but I see a Yod is being made of four planets/points, because there is always a 4th release point, which is cumulated in a transit or there is almost always something there in the chart, in the release point, such as an important asteroid. No Yod would miss a 4th leg, its release point.
• It's a highly fated structure, pointing to a special mission in this life, perhaps the cumulus of several lifetimes. The preparation continues in this life and there is a "gestation" period. The Yod cannot be triggered before its time.

The Yod is triggered by transits, most likely on at least two points, and one of them has to be the apex. I suspect, however, that all three (if not four) are transited when the Yod is triggered.

• Currently, I don't consider the apex as the result – the trigger is the “Finger of God”, where God “points” (and we see God here as fate, the timing and nature of the event) – but I see it as an arrow-like structure and like all arrow-like structures, the apex is actually the maximum tension of the bow (the nocking point) before releasing the arrow.
• The "result" is the lightening of the whole structure (compared to a crystal prism) with emphasis on the dance of the opposition. The opposition is at the core of the result. The Yod is a "hugging" structure - the energy comes from the apex - a laser beam through the apex - and "hugs" the whole structure, especially the release point. If a person is there, at the release point, it's the primary beneficiary, returning the energy through the mirror of the opposition and the harmonious dance of the sextile, to the "hugger", in a perpetual dance (just like oppositions are, like a tango)
• The preparation is made through the sextile, the only part of the Yod which is in the hands of the protagonist(s); the trigger (apex - the transit) is not in our hands; in a synastry, however, the apex person plays the role of "God", the trigger (the one with the bow, the one releasing the arrow).
• Unlike other astrologers, I don't believe the apex has to be a "more" personal planet, the sextile is the personal part of the Yod, by sign and house and rulers - of course, a generational sextile such as Neptune sextile Pluto has its own personal value based on the chart; the trigger can be any planet. From another perspective, clearly the entire Yod is personal, for the accumulated energy manifesting as a “fated” event, by the laws of karma, is of our own doing.
• The Yod is always a turning point, a major change, usually consisting of a series of events.
• The result (all points lit by the laser beam), the illuminated crystal, has a permanent value, there is no return to the previous status, an "evolutionary step" as it has been described by Marchisone
• The Yod needs planetary energy to be triggered. A Yod involving nodes or angles is dormant, well all Yods are, until planets hit the Yod. An astrobody needs to conjunct the angle/node on one side at least for the Yod to be triggered,  the axis itself is not enough.  If the apex is an angle/node, the Yod is about the whole axis, logically. For example, a Yod with an ASC as apex hit by Pluto on ASC will result in a major transformation/turning point on the ASC/DSC axis, the preparation for it being the sextile. The "primary" result will be connected to relationships (DSC), the "secondary" result will be on ASC, as a mirroring effect of the opposition. The whole axis will be lit.
• The Yod is basically a midpoint structure - the midpoint of a sextile - so the sextile is major in a Yod - it's a whole meditation and poetry about the sextile as an aspect here, in the Yod. If we want to understand sextiles, we need to integrate and understand quincunx energy as well. The opposition and the sextile create a Cross structure and all four planets are reunited: the two planets in the sextile are joined, so are the other two, on the opposition axis.
• Although sometimes the opposition to the apex appears non-existent, it IS there; either as a major midpoint, an asteroid showing the mission, or an outer planet transiting slowly over there, as said at one of the previous points.
• Yods have an "in-house" impact, the release highlights an entire house rather than a planet/point. In this case, all planets/asteroids/midpoints in the release house will be somehow related to the Yod and one can say everything that happens in that native’s house will offer clues about the Yod evolution. All Yods will happen on a house axis, such as 1st/7th house Yods, and this will be the primary manifestation of the Yod, considering houses are how we manifest zodiac energy in the real plane and in a particular area of our life.

 

Photo: A vision of the possible energetic impact of a triggered Yod.