A transparent square sheet contains a pattern. If the sheet is folded along…

Concept: On a transparent sheet, folding along a marked line reflects every stroke in the folded-away portion across that line and superimposes it on the retained portion, because ink on a transparent sheet stays visible through the fold. The visible result is the union of whatever strokes were already in the retained portion and the mirror image of whatever strokes were in the folded-away portion.

Application: Here the fold line runs horizontally, so the lower portion folds up onto the upper (retained) portion, reflecting every line of the lower portion about that line. The star-shaped outer zig-zag reflects onto the upper boundary's own zig-zag, and the two internal strokes plus the two diagonal rays that sit only in the lower portion of the source figure reappear, mirrored, inside the retained portion, running outward from the crown's base toward its two lower corners.

Cross-check: Reflecting the retained portion's own outline back across the fold line reproduces the source figure's lower portion exactly — same outer zig-zag, same two internal strokes, same two diagonal rays — confirming no stroke was duplicated or dropped in the fold.

Result: the crown-shaped outline is carried over unchanged, and the lower portion's own two internal strokes together with its two diagonal rays reappear, mirrored, beneath it — matching the source figure's lower portion stroke for stroke.