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Four triangles meeting at the center — the essential unit for star points, hourglasses, and pinwheels
Also known as: Hourglass
The quarter-square triangle unit contains four right triangles meeting at the center — essentially two half-square triangles sewn together on the remaining diagonal. It's the unit that makes Ohio Stars, Hourglass blocks, and hundreds of other classic patterns possible.
| Fabric | Cut | For |
|---|---|---|
| Dark | 1 square at 7¼″ | dark squareseach pair makes 2 finished 6″ hourglass units — trim to 6½″ |
| Light | 1 square at 7¼″ | light squareseach pair makes 2 finished 6″ hourglass units — trim to 6½″ |
HST-first: make two HSTs, place them RST with seams nested and opposite fabrics facing, cut the crossing diagonal, sew ¼″ each side.
The quarter-square triangle is not typically named as a distinct block — it's a construction unit, the building block behind dozens of named patterns. Wherever you see a square divided into four triangles (the Hourglass, the X block, the X-and-Plus), you're looking at quarter-square triangle construction.
As a practical technique, QSTs emerged as quilters became more systematic about using right-triangle geometry to create complex patterns without set-in seams. The two-step process — make HSTs, then sew two HSTs together on the remaining diagonal — was documented in quilting texts by the mid-19th century and became standard practice by the 1880s.
The most important modern application is in star blocks. The Ohio Star's eight crisp points are created by four QST units, each contributing two triangle halves to adjacent star points. The technique for making QSTs from squares (the "2-at-a-time HST then QST" method) is now one of the most important precision skills in quilting — it appears in patterns at every level of complexity.
Make two half-square triangle units using your chosen fabrics. For a 4" finished QST, cut squares at 5¼" — the QST formula is finished size + 1¼" (not the HST formula of +⅞"). Make two HSTs at this size.
Place two HSTs right-sides-together with opposite fabrics touching (light against dark). The diagonal seams should run in opposite directions. They will nest cleanly for accurate sewing.
Draw a diagonal line perpendicular to the existing seam (from corner to corner, crossing the seam). Sew ¼" on each side of this new line.
Cut on the drawn diagonal. Press seams open. You now have two QST units from each pair of HSTs.
Use a square ruler to trim each QST to the exact size needed. A QST for a 12" Ohio Star should be trimmed to 4½" (finished 4"). Line up the diagonal line on your ruler with the center seam intersection.
QST units are usually paired — two of the same unit appear in each pattern position. Keep this pairing in mind when choosing fabrics: the unit that becomes the star point should use two colors that create visual contrast both within the unit and against the neighboring units.
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Four QST units assembled into a square, creating an hourglass or bowtie shape.
The most common use of QSTs in traditional quilting — four QST units forming the eight points of an Ohio Star.
QST units arranged to create an X or plus-sign shape depending on color placement.
NiftyFifty quilters have been swapping blocks like this one since 1997. Browse our historical archive or join a new swap.
Browse quilt swaps →Eight crisp star points emerge from four quarter-square triangle units — a pattern that rewards precise piecing
The most versatile unit in patchwork — master this and you can make hundreds of different quilt patterns
Four flying geese units form four star points around a center square — a step up from Ohio Star in visual complexity
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