Jacob's ladder quilt block

How the block is built

The block is a 3 × 3 grid of units; each unit is a third of the block, and each small square in a four-patch is a sixth. In a 12-inch block the units are 4 inches and the small squares 2 inches.

All five four-patches are turned the same way, with their dark squares running from top left to bottom right. That lines them up into the ladder along the block's main diagonal. The triangles are turned so their medium halves point toward the other two corners: on the top and right sides the medium half is in the top-right half of the unit, and on the left and bottom sides it's in the bottom-left half. The light halves of the triangles all face the ladder.

Cutting chart (one block)

The small squares are half the unit + ½ inch. The HST squares are the unit + ⅞ inch (exact) or + 1 inch (to trim); two pairs make the four HSTs. The strip lengths are exactly ten segments' worth, so cut them a couple of inches longer to square up the end. All sizes were checked by calculation. The 12-inch block cuts from 2½-inch strips, which makes it a natural fit for a jelly roll plus a background.

Step 1: strip-piece the four-patches

1. Sew the dark strip to the light strip along the long edge. Press toward the dark.
2. Square up one end and cut ten segments the strip width (1½, 2 or 2½ inches).
3. Take two segments, turn one end for end so dark is against light, and put them right sides together. The pressed seams face in opposite directions and nest. Sew along the long edge.
4. Press the new seam to one side (or open). Make five four-patches. Each should measure the unit + ½ inch.

Step 2: make the half-square triangles

1. Draw a diagonal on the wrong side of each light HST square and pair it with a medium square.
2. Sew ¼ inch on both sides of the line, cut on the line, press toward the medium.
3. Trim to the unit + ½ inch (2½, 3½ or 4½ inches). The half-square triangle guide shows trimming in detail.

Step 3: assemble the block

1. Lay out the nine units. Turn every four-patch with a dark square in its top-left corner.
2. Place the HSTs: top and right sides with the medium in the top-right half, left and bottom sides with the medium in the bottom-left half.
3. Sew the rows. Press toward the HSTs in every row; in the outer rows that pushes seams toward the center, in the middle row away from it, so they nest.
4. Join the rows. Press the long seams toward the middle row.
5. Measure: 6½, 9½ or 12½ inches.

Common mistakes and fixes

Quilts made from Jacob's ladder

Turning every other block a quarter turn is the layout that gives the block its reputation. The ladders then run in both diagonal directions, and the red triangles of four neighboring blocks meet in large squares on point. With every block turned the same way, the ladders all run one direction and the triangles make diagonal stripes; that's calmer and still handsome. Try both on the floor before sewing the rows.

The block is a classic scrap user, since every four-patch can be a different dark. Keep the triangles in one medium fabric and the background consistent, and the structure holds no matter how many darks you use.

Related blocks

The four-patch ladder idea is the same one behind the Irish chains; see the single Irish chain. The churn dash and card trick are other nine-patches with triangles. For HSTs at other sizes use the half-square triangle calculator, and for a different block size the quilt block resizer. The quilt block library lists every block on the site.

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