What is 2-String Kite? How to Solve Sudoku

What it is

Use one digit, with one row and one column where it has only two spots (the two strings of a kite).

One end of the row and one end of the column sit in the same box. They can't both be the digit, so one of the other two ends (the kite's tips) must be.

Any cell that sees both tips can't be that digit.

How to spot it

Pick one digit, find a row and a column with exactly two spots each, and check whether one end of each meets in the same box.

Example

Yellow cells are where to look, orange cells are the reason, red digits are candidates you can remove, and the blue digit is the answer.

Think about 7 only. In row 3, 7 fits only in R3C4 or R3C8; in column 5, only in R2C5 or R6C5. R3C4 and R2C5 share box 2, so they can't both be 7. That means R3C8 or R6C5 must be 7. Any cell that sees both (R6C8) can't be 7.