While doing a puzzle I had, twice, an X-wing come up where 3 of the boxes held the same 2 candidates and the 4th box contained the same 2 candidates plus one more. On a whim I tried making the box with the 3 candidates the number that was the odd one and it worked. Twice.

Example: r1c1 has candidates 1 and 5 ***** r1c3 has candidates 1 and 5 ***** r6c1 has candidates 1 and 5 ***** r6c3 has candidates 1, 5 and 9.

I made r6c3 a 9 and it worked (because the other 3 held identical candidates). It worked a 2nd time on another X-wing on the same puzzle.

Was this just a fluke or is this an actual solving technique?

Thank you.

Camchase