Step 1

Take a square sheet, lay it flat on the table, with the bottom edge horizontal.

additional information

  • If the paper is two-colored, place the colored side facing up.
  • The corners of the square are: top left, top right, bottom right, and bottom left.

Step 2

Make a vertical valley fold by bringing the right edge over to the left edge.

Crease firmly, then unfold.

Step 3

Make a horizontal valley fold by bringing the bottom edge up to the top edge.

Crease firmly, then unfold.

additional information

  • These folds mark the medians of the original square.

Step 4

Turn the paper over from right to left, then rotate it into a diamond position.

additional information

  • The corners are now: top, right, bottom, and left.

Step 5

Make a vertical valley fold by bringing the right corner over to the left corner.

Crease firmly, then unfold.

Step 6

Make a horizontal valley fold by bringing the top corner down to the bottom corner.

Crease well, and leave it folded.

additional information

  • You now have two triangular flaps stacked together, connected by a horizontal hinge at the top.
  • On both the front and back faces, two valley folds connect the middle of the hinge edge to the middle of the right and left sides of the triangular flaps.

Step 7

Hold the model between the thumbs and index fingers of both hands:

additional information

  • The thumbs, in front, touch the middle of the front valley folds.
  • The index fingers, at the back, touch the middle of the back valley folds.
  • The fingers of the right hand are just to the right of the right valley folds.
  • The fingers of the left hand are just to the left of the left valley folds.
  • The model is no longer on the table: it is held vertically in front of you, with the hinge edge horizontal and the third point of the triangle pointing downward toward the table.

Step 8

Give the model volume. Push both hands downward symmetrically until the thumbs and index fingers meet.

additional information

  • The model opens, forming four double-layered triangular flaps:
  • one in the left hand,
  • one in the right hand,
  • one free toward the front,
  • one free toward the back.

Step 9

Tilt the front flap to the left and hold it against the left flap.

Step 10

Tilt the back flap to the right and hold it against the right flap.

Step 11

Place the model flat on the table; the water bomb base is now complete.

additional information

  • You have a triangular shape with:
  • a closed tip at the top,
  • four double-layered triangular flaps open at the bottom.
  • You can feel a vertical valley fold running from the closed tip to the middle of the bottom edge: this is the vertical axis of symmetry.
  • The four flaps are connected by the closed tip at the top and by this axis of symmetry:
  • front left flap,
  • back left flap,
  • front right flap,
  • back right flap.