Copyright © Kevin Stone

R2C7 is the only square in row 2 that can be <7>

R3C2 is the only square in row 3 that can be <7>

R3C3 is the only square in row 3 that can be <4>

R3C4 is the only square in row 3 that can be <8>

R8C4 can only be <7>

R9C8 is the only square in row 9 that can be <7>

R2C4 is the only square in column 4 that can be <9>

Intersection of row 2 with block 2. The value <1> only appears in one or more of squares R2C4, R2C5 and R2C6 of row 2. These squares are the ones that intersect with block 2. Thus, the other (non-intersecting) squares of block 2 cannot contain this value.

R3C6 - removing <1> from <156> leaving <56>

Intersection of column 1 with block 1. The value <3> only appears in one or more of squares R1C1, R2C1 and R3C1 of column 1. These squares are the ones that intersect with block 1. Thus, the other (non-intersecting) squares of block 1 cannot contain this value.

R1C2 - removing <3> from <356> leaving <56>

Intersection of column 1 with block 7. The value <8> only appears in one or more of squares R7C1, R8C1 and R9C1 of column 1. These squares are the ones that intersect with block 7. Thus, the other (non-intersecting) squares of block 7 cannot contain this value.

R8C3 - removing <8> from <589> leaving <59>

Intersection of column 4 with block 5. The value <5> only appears in one or more of squares R4C4, R5C4 and R6C4 of column 4. These squares are the ones that intersect with block 5. Thus, the other (non-intersecting) squares of block 5 cannot contain this value.

R4C6 - removing <5> from <245> leaving <24>

R6C6 - removing <5> from <1256> leaving <126>

Intersection of column 8 with block 3. The value <5> only appears in one or more of squares R1C8, R2C8 and R3C8 of column 8. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.

R1C9 - removing <5> from <2569> leaving <269>

R2C9 - removing <5> from <256> leaving <26>

Squares R5C1<12>, R5C2<19> and R5C8<29> in row 5 form a comprehensive locked triplet. These 3 squares can only contain the 3 possibilities <129>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.

R5C5 - removing <1> from <146> leaving <46>

R5C9 - removing <29> from <2469> leaving <46>

R2C5 is the only square in column 5 that can be <1>

R6C6 is the only square in column 6 that can be <1>

Intersection of column 9 with block 3. The value <2> only appears in one or more of squares R1C9, R2C9 and R3C9 of column 9. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.

R1C8 - removing <2> from <259> leaving <59>

Squares R1C2, R1C5 and R1C9 in row 1, R5C5 and R5C9 in row 5 and R9C2 and R9C5 in row 9 form a Swordfish pattern on possibility <6>. All other instances of this possibility in columns 2, 5 and 9 can be removed.

R2C9 - removing <6> from <26> leaving <2>

R7C2 - removing <6> from <1469> leaving <149>

R1C1 is the only square in row 1 that can be <2>

R5C1 can only be <1>

R5C2 can only be <9>

R5C8 can only be <2>

R1C5 is the only square in row 1 that can be <3>

R2C1 is the only square in row 2 that can be <3>

R8C7 is the only square in row 8 that can be <1>

R3C7 can only be <6>

R3C6 can only be <5>

R6C7 can only be <3>

R1C9 can only be <9>

R6C2 can only be <5>

R6C8 can only be <8>

R4C8 can only be <9>

R1C8 can only be <5>

R3C8 can only be <1>

R2C6 can only be <6>

R4C7 can only be <4>

R7C8 can only be <3>

R6C3 can only be <2>

R1C2 can only be <6>

R4C2 can only be <3>

R6C4 can only be <6>

R4C3 can only be <8>

R7C4 can only be <2>

R5C5 can only be <4>

R4C4 can only be <5>

R9C2 can only be <4>

R2C3 can only be <5>

R8C3 can only be <9>

R7C6 can only be <4>

R4C6 can only be <2>

R7C7 can only be <9>

R5C9 can only be <6>

R8C5 can only be <8>

R7C2 can only be <1>

R8C6 can only be <3>

R7C3 can only be <6>

R8C1 can only be <5>

R9C5 can only be <6>

R9C9 can only be <5>

R9C1 can only be <8>

R8C9 can only be <4>