Traditional pattern, public domain. Also known as Virginia Reel; documented from the mid-1800s onward.
A mesmerizing spiral block created by surrounding a center square with progressively larger half-square triangle units in alternating colors. The spiraling effect is one of the most striking visual illusions in traditional quilting.
Snail's Trail has been documented since the mid-1800s and is one of the most visually complex traditional blocks despite using only squares and half-square triangles. The spiraling design mimics the logarithmic spiral found in snail shells, making it a remarkable example of mathematical beauty in folk art.
Known as Virginia Reel in some regions (referencing the spiraling folk dance), the block demonstrates how quilters intuitively understood geometric progression long before formal mathematical education was common. The block was popular across all regions of the United States and remains a favorite among both traditional and modern quilters.
Also known as: Virginia Reel, Monkey Wrench (in some regions), Indiana Puzzle, Ocean Wave
finished Block Size
12 inches
seam Allowance
1/4 inch
grid Basis
Progressive rounds from center outward (center + 3 rounds)
units Required
1 center four-patch, 4 small HSTs (round 1), 4 medium HSTs (round 2), 4 large HSTs (round 3)
All measurements include 1/4" seam allowance unless noted.
| Piece | Fabric | Cut Size | Qty | Notes |
|---|---|---|---|---|
| A | Dark | 2 x 2 inches | 2 | Center four-patch squares |
| A | Light | 2 x 2 inches | 2 | Center four-patch squares |
| B | Dark | 2 3/8 x 2 3/8 inches | 2 | Cut once diagonally for round 1 HSTs |
| B | Light | 2 3/8 x 2 3/8 inches | 2 | Cut once diagonally for round 1 HSTs |
| C | Dark | 4 1/4 x 4 1/4 inches | 2 | Cut once diagonally for round 2 HSTs |
| C | Light | 4 1/4 x 4 1/4 inches | 2 | Cut once diagonally for round 2 HSTs |
| D | Dark | 7 x 7 inches | 2 | Cut once diagonally for round 3 HSTs |
| D | Light | 7 x 7 inches | 2 | Cut once diagonally for round 3 HSTs |
Sew a dark 2-inch square to a light 2-inch square. Repeat for the second pair. Press seams toward the dark. Join the two pairs into a four-patch with darks on opposite corners. Press the center seam open. The four-patch should measure approximately 3 1/2 inches (will be trimmed later).
Tip: Place dark squares diagonally opposite each other — this establishes the spiral direction.
Sew a dark round-1 triangle to one side of the four-patch, aligning the long edge of the triangle with one side. Sew the opposite dark triangle to the other side. Press outward. Then sew light triangles to the remaining two sides. Press outward. Trim to 4 3/4 inches square.
Tip: The key: dark triangles go on the sides adjacent to the light squares of the four-patch, and light triangles go adjacent to the dark squares. This creates the spiral.
Following the same spiral logic, sew dark round-2 triangles to the sides where light fabric is dominant, and light triangles where dark fabric is dominant. Press outward after each addition. Trim to 8 inches square.
Continue the spiral: sew dark round-3 triangles to the light-dominant sides, and light triangles to the dark-dominant sides. Press outward. Trim carefully to 12 1/2 inches square.
Use a 12 1/2 inch square ruler to trim the block precisely. Step back and verify the spiral reads correctly — you should see a clear clockwise (or counterclockwise) spiral of alternating dark and light triangles expanding from the center.
See how this traditional pattern looks in different color combinations.
Edge to edge, alternating clockwise and counterclockwise spirals — 5x5 blocks for a 60 x 60 inch quilt
All blocks spiraling the same direction for a cohesive swirl effect
Four blocks rotated to create a large central spiral motif for a wall hanging