Windowpane Plaid
Structure
The windowpane pattern is just a grid — single thin lines (sometimes double lines) running vertically and horizontally at regular intervals over a plain background. The spaces between the lines are large relative to the line width, which gives the pattern its open, airy quality. Unlike glen plaid or tartan, there is no complexity in the weave at the intersections. The lines simply cross.
In Tailoring
Windowpane is overwhelmingly a suiting and tailoring pattern. It appears most often in men's suits, sport coats, and trousers. The pattern's simplicity allows it to be dressed up or down more easily than busier plaids. A navy suit with a gray windowpane overcheck is a classic combination that works in business settings without being as bold as a full glen plaid.
The width of the grid spacing affects how formal the pattern reads. A widely-spaced windowpane on a dark background is subtle and appropriate for conservative business environments. A more tightly spaced or brightly colored windowpane becomes bolder and more fashion-forward.
Windowpane vs. Graph Check
When the grid lines are very closely spaced — creating small, tight squares — the pattern is usually called a "graph check" rather than a windowpane. The distinction is a matter of scale rather than structure. Graph check is denser and busier; windowpane is open and spare.
Styling
Because of its simplicity, windowpane is one of the easier patterns to combine with other patterns. A windowpane suit can be worn with a striped shirt and a solid tie, or even with a patterned tie, without overwhelming the outfit. For guidance on combining patterns, see How to Mix Plaid Patterns.