Level 220 solution

Solver-verified route

1. Place Piece 1 at column 7, row 3.
2. Place Piece 5 at column 2, row 5.
3. Place Piece 2 across column 5 row 1, column 6 row 1, column 5 row 2.
4. Place Piece 4 across column 2 row 6, column 3 row 6, column 2 row 7.
5. Place Piece 3 across column 3 row 4, column 4 row 4, column 5 row 4, column 5 row 5.
6. Place Piece 6 across column 5 row 3, column 6 row 3, column 6 row 4.

Part of the "Final columns" chapter. The solver certified 720 solving lines with 87% of in-between placements being dead ends, for a difficulty score of 18.0 (grade 4 of 5).