Which crease pairs every mark?
A shape may look balanced until one mark has no twin. Learn the fold test, then check a brand-new pattern.
A fold compares two sides
A reflection fold pairs points at equal distances across one line. A point right on the crease stays in place—it is its own reflection.
Slide a point; its twin follows
Move one point beside a practice crease. Its reflected twin stays equally far on the other side and at the same height.
The outline is not enough
Try three unrelated patterns. A proposed axis works only if every mark has a reflected partner.
Fold marks onto their partners
Close a simple vertical practice fold. Matching marks land together; one missing twin would remain exposed.
A new pattern, three fair choices
Vertical, horizontal, and upper-left-to-lower-right diagonal creases use the same color and weight. Check every mark, not just the outside box.
Commit before the new setup runs.
Which fold line makes EVERY mark land on a twin?
Fold the marked sheet along the tested crease.
