Solution to Challenge 3

The boat, first three folds, written as diagram steps (your wording will differ)

Step 1 (book fold, then unfold)
- Line: valley fold across the middle, top edge down to bottom edge.
- Arrow: there and back (fold and unfold).
- Picture afterwards: an open rectangle with a horizontal crease through the centre.

Step 2 (book fold again, kept folded)
- Line: valley fold along the same crease.
- Arrow: top edge down to the bottom edge, and stay folded.
- Picture afterwards: a half-height rectangle with the fold at the top.

Step 3 (corners in, a variation on the blintz idea, done at the top only)
- Line: two valley fold lines, one at each top corner.
- Arrows: both top corners fold down to the centre of the folded edge.
- Picture afterwards: a house shape, a triangle roof with a strip of paper along the bottom.

Checkpoint: if someone else can fold the house shape from your list alone, your diagram description is clear. Gaps to look for: forgetting to say which layer to fold, and missing the "fold and unfold" in step 1.