Sudoku Players' Forum (clone)

https://imgur.com/a/aAZsTf9

Grateful your advice as to why this fails.
Tks

Hm, this is so far from being a swordfish, that i guess, that you don't know it's definition:
If a digit in 3 rows (or columns resp.) is restricted to (only appears in) 3 columns (rows), you can eliminate it from the other cells of that columns (rows).
(wherever you place it in the 3 rows, you also already occupy the 3 columns)

Here the 7 is neither restricted to 3 columns in rows 348 nor to 3 rows in columns 178.

btw there are 2 skyscrapers for digit 9 (in r28 or c28), which solve the puzzle.

Hi eleven,
Your reply much appreciated.
You are correct in that my interpretation of the necessary conditions was incorrect.
Now its onto skyscrapers....

duplicate deleted

Here are some links for skyscrapers:
hodoku solving techniques
sudopedia
or look at
Strong Links for Beginners
For many solvers skyscrapers are a special case of finned x-wings, which in turn are grouped skyscrapers.