2 Strong Links
2 Strong Links is the general case of the strong-links family — two conjugate pairs on the same digit in any combination of houses where one cell from each pair sees the other. The bridge cells can't both hold the digit, so at least one opposite endpoint must, eliminating the digit from any cell that sees both endpoints.
What are 2 Strong Links?
2 Strong Links is a single-digit construction built from two conjugate pairs — two houses where a particular candidate appears in exactly two cells. The houses can be any mix of rows, columns, and blocks, provided one cell from each pair shares a line with a cell from the other. Those two shared-line cells are the bridge: because they see each other, they can't both hold the digit. Since each conjugate pair must place the digit in one of its two cells, and the bridge can't supply both, at least one of the other two endpoints has to contain the digit. Any cell outside the construction that shares a house with both of those endpoints can't also hold the digit, so it gets eliminated.
How to spot it
For one digit, find two conjugate pairs in rows, columns, or boxes. Verify a weak inference between one candidate from each pair: those connector candidates must see each other and cannot both be true. The other pair members are the endpoints. A target is valid only when it sees both endpoints. Skyscraper and 2-String Kite are named restrictions of this same two-node AIC.
The logic
Each conjugate pair is a house where the digit has exactly two candidate cells, so one of them must be the digit. In a 2 Strong Links construction, one candidate from each pair sits on a shared line — the bridge. Because the two bridge cells see each other, at most one of them can be the digit. If the first bridge cell is the digit, the second pair's digit falls on its opposite endpoint. If the second bridge cell is the digit, the first pair's digit falls on its opposite endpoint. And if neither bridge cell is the digit, both opposite endpoints must be. In every case, at least one opposite endpoint contains the digit, so any cell that sees both endpoints can't also hold it. The same reasoning holds regardless of which combination of houses the two pairs live in.