Three cells in one straight column
Trace BOX from row 5, column 1, then continue downward through row 6, column 1 and finish at row 7, column 1. The letters read B → O → X in one straight segment, so there is no turn to remember.
For a numbered check, use 1 at row 5, column 1; 2 at row 6, column 1; 3 at row 7, column 1. This route spans three rows, stays within one column, and visits an edge cell on every step.