Practise the XY-Wing

A pivot and two pincers. Whichever way the pivot falls, one pincer takes the digit.

8 real positions, each taken from an actual puzzle at the moment this was the cheapest move available. Two steps: find the cells that form the pattern, then find the candidate it rules out. A near miss tells you how many you had right, so getting it wrong is worth something.

Select the cells that form the pattern, then check. 1 / 8

9	2	4	18	7	6	3	5	18
8	1	7	3	5	9	6	2	4
3	6	5	4	2	18	78	17	9
2	5	1	6	8	3	4	9	7
7	4	3	9	1	2	5	8	6
6	8	9	7	4	5	1	3	2
5	9	2	18	6	178	78	4	3
1	7	8	2	3	4	9	6	5
4	3	6	5	9	78	2	17	18

How to spot it

Find bivalue cells — usually few enough to list. For each, check the bivalue cells it can see for the {X,Z} / {Y,Z} shape. Then look at what those two pincers jointly see.

Full explanation on the XY-Wing reference page.

Practise something else

XYZ-Wing An XY-Wing whose pivot holds all three digits, so targets must see all three cells.
X-Wing One digit, two rows, two columns. The first pattern that spans the whole grid.
XY-Chain A run of two-candidate cells that returns to the same digit at both ends.

9	2	4	18	7	6	3	5	18
8	1	7	3	5	9	6	2	4
3	6	5	4	2	18	78	17	9
2	5	1	6	8	3	4	9	7
7	4	3	9	1	2	5	8	6
6	8	9	7	4	5	1	3	2
5	9	2	18	6	178	78	4	3
1	7	8	2	3	4	9	6	5
4	3	6	5	9	78	2	17	18

9	2	4	18	7	6	3	5	18
8	1	7	3	5	9	6	2	4
3	6	5	4	2	18	78	17	9
2	5	1	6	8	3	4	9	7
7	4	3	9	1	2	5	8	6
6	8	9	7	4	5	1	3	2
5	9	2	18	6	178	78	4	3
1	7	8	2	3	4	9	6	5
4	3	6	5	9	78	2	17	18

9	2	4	18	7	6	3	5	18
8	1	7	3	5	9	6	2	4
3	6	5	4	2	18	78	17	9
2	5	1	6	8	3	4	9	7
7	4	3	9	1	2	5	8	6
6	8	9	7	4	5	1	3	2
5	9	2	18	6	178	78	4	3
1	7	8	2	3	4	9	6	5
4	3	6	5	9	78	2	17	18