Half-square triangle

A square pieced from two triangles.

Also known as: HST unit, Two triangle square

Clothing & laundryCulturalQuiet profile

Meanings

A half-square triangle is a pieced quilt unit made from two right triangles joined along their long edges to form a square, and is among the most used units in patchwork.

Culturally establishedVerified fact
Is a square pieced from two right triangles joined along their long edges.
Contexts: History
Culturally establishedVerified fact
Combines into a very large number of traditional blocks, which is why patchwork instruction teaches the unit before any block that uses it.
Contexts: History

Visual description

A square divided corner to corner by a single diagonal seam into two triangles of contrasting fabric.

A fuller structured visual breakdown is not yet documented for this symbol.

Confidence

IdentityModerate confidence: Moderate confidence because the identity is documented in encyclopedic references, but only a single source has been found so far.
Historical originLow confidence: Low confidence because the historical origin is documented in encyclopedic references, but only a single source has been found so far, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useModerate confidence: Moderate confidence because the current use is documented in encyclopedic references, but only a single source has been found so far.
Visual matchModerate confidence: Moderate confidence because the visual match is documented in encyclopedic references, but only a single source has been found so far.

Sources

Pattern (sewing)
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional description of a mark, its usual name and where it is encountered. Where an issuing body defines the mark, that body is cited alongside and governs.

Last reviewed 2026-08-24

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Meanings

A half-square triangle is a pieced quilt unit made from two right triangles joined along their long edges to form a square, and is among the most used units in patchwork.

Culturally establishedVerified fact

Is a square pieced from two right triangles joined along their long edges.

Contexts: History

Culturally establishedVerified fact

Combines into a very large number of traditional blocks, which is why patchwork instruction teaches the unit before any block that uses it.

Contexts: History

Confidence

IdentityModerate confidence: Moderate confidence because the identity is documented in encyclopedic references, but only a single source has been found so far.
Historical originLow confidence: Low confidence because the historical origin is documented in encyclopedic references, but only a single source has been found so far, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useModerate confidence: Moderate confidence because the current use is documented in encyclopedic references, but only a single source has been found so far.
Visual matchModerate confidence: Moderate confidence because the visual match is documented in encyclopedic references, but only a single source has been found so far.