2-String Kite

A very short single-digit chain where one end must be true

Unique Rectangle Type 1

Find the basic deadly pattern and take advantage of it

Unique Rectangle Type 2

Adds an extra candidate in two cells

Unique Rectangle Type 3

Unique Rectangle combined with a Naked or Hidden Pair

Unique Rectangle Type 4

Unique Rectangle considering the unique candidates within the unit

Bi-value Universal Grave

If all remaining cells have only two candidates, this Sudoku is fatally flawed