The saltire is important both in heraldry, being found in many coats of arms, and in vexillology, being found as the dominant feature of multiple flags.

The saltire is one of the so-called ordinaries, geometric charges that span throughout (from edge to edge of) the shield. As suggested by the name saltire ("stirrup"; in French: sautoir, in German: Schragen), the ordinary in its early use was not intended as representing a Christian cross symbol. The association with Saint Andrew is a development of the 15th to 16th centuries. The Cross of Burgundy emblem originates in the 15th century, as a field sign, and as the Saint Andrew's Cross of Scotland was used in flags or banners (but not in coats of arms) from the 16th century, and used as naval ensign during the Age of Sail.

When two or more saltires appear, they are usually blazoned as couped (cut off). For example, contrast the single saltire in the arms granted to G. M. W. Anderson —with the three saltires couped in the coat of Kemble Greenwood.

Diminutive forms include the fillet saltire, usually considered half or less the width of the saltire, and the saltorel, a narrow or couped saltire.

A field (party) per saltire is divided into four areas by a saltire-shaped "cut". If two tinctures are specified, the first refers to the areas above (in chief) and below (in base) the crossing, and the second refers to the ones on either side (in the flanks). Otherwise, each of the four divisions may be blazoned separately.

The phrase in saltire or saltirewise is used in two ways:
199 Two long narrow charges "in saltire" are placed to cross each other diagonally. Common forms include the crossed keys found in the arms of many entities associated with Saint Peter and paired arrows.
299 When five or more compact charges are "in saltire", they are arranged with one in the center and the others along the arms of an invisible saltire.
Division of the field per saltire was notably used by the Aragonese kings of Sicily beginning in the 14th century (Frederick the Simple), showing the pales of Aragon and the "Hohenstaufen" eagle (argent an eagle sable).
The Flag of Scotland, called The Saltire or Saint Andrew's Cross, is a blue field with a white saltire. According to tradition, it represents Saint Andrew, who is supposed to have been crucified on a cross of that form (called a crux decussata) at Patras, Greece.

The …

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Anne Roes (1937) identifies a design consisting of two crossing diagonal lines in a rectangle, sometimes with four dots or balls in the four quarters, as an emblem or vexillum (standard) of Persepolis during the 3rd to 2nd centuries BC. Roes also finds the design in Argive vase painting, and still earlier in button seals of the Iranian Chalcolithic. Roes also notes the occurrence of a very similar if not identical vexillum which repeatedly occurs in Gaulish coins of c. the 2nd to 1st century BC, in a recurring design where it is held by a charioteer in front of his human-headed horse. A large number of coins of this type (118 out of 152 items) forms part of the Les Sablons hoard of the 1st century BC, discovered in Le Mans between 1991 and 1997, associated with the Cenomani.

The same design is found on coins of Christian Roman emperors of the 4th to 5th centuries (Constantius II, Valentinian, Jovian, Gratianus, Valens, Arcadius, Constantine III, Jovinus, Theodosius I, Eugenius and Theodosius II). The letter Χ (Chi) was from an early time used as a symbol for Christ (unrelated to the Christian cross symbol, which at the time was given a T-shape). The vexillum on imperial coins from the 4th century was sometimes shown as the Labarum, surmounted by or displaying the Chi-Rho monogram rather than just the crux decussata. The emblem of the crux decussata in a rectangle, sometimes with four dots or balls, re-appears in coins the Byzantine Empire, in the 9th to 10th centuries. Roes suggested that early Christians endorsed its solar symbolism as appropriate to Christ.
• Reconstruction of Saltire pattern labarum per A.Roes
• Gold stater of the Cenomani, on the reverse an androcephalous horse led by a charioteer extending a vexillum in front of it, riding over a fallen enemy.
• Coin of Theodosius I (393–395), with a vexillum displaying a crux decussata
• Coin of Theodosius II (425–429), showing the emperor with globus cruciger and with the same vexillum
The association with Saint Andrew develops in the late medieval period. The tradition according to which this saint was crucified on a decussate cross is not found in early hagiography. Depictions of Saint Andrew being crucified in this manner first appear in the 10th century, but do not become standard before the 17th century. Reference to the saltire as "St Andrew's Cross" is made by the Parliament of Scotland (where Andrew had been adopted as patron saint) in 1385, in a decree to the effect that every Scottish and French soldier (fighting against the English under Richard II) "shall have a sign before and behind, namely a white St. Andrew's Cross".
• Saint Andrew martyred on a decussate cross (miniature from an East Anglian missal, c. 1320)
• Saint Andrew holding his cross on a Taler of Ernest Augustus, Elector of Brunswick-Lüneburg (1688)
The cross continues to be used in modern times by religious groups. The arms of the Episcopal Church in the United States features a saltire in its canton. The logo of the Christian Church (Disciples of Christ) features a red chalice with a Saint Andrew's cross, representing the Scottish heritage of the denomination.

• Gules a saltire argent (Neville)
• Azure a saltire or (Saint Alban's Cross, St Albans 1634)
• Argent a saltire azure (Katwijk)
• Per saltire azure and argent, a saltire gules (Gage of Hengrave)
• Argent on a saltire engrailed sable nine annulets of the field (Earl of Scarsdale)
• Quarterly 1st & 4th: Barry of six [seven] vair and gules; 2nd & 3rd: Gules, a saltire vair (Henry Beaumont of Devon, d.1591)
• Argent a saltire floretty gules (Busséol)
• Gules a fillet saltire couped argent above a wheel of the same (Klein-Winternheim)
• Coat of arms of the San Andrés Archipelago
• Hexham Coat of Arms (1953)
saltirewise
• Gules two keys in saltire argent and or (Coats of arms of the Holy See and Vatican City)
• Gules a cross saltire and orle of chains linked together or, in the fess point an emerald vert (Kingdom of Navarre)
• Gules two keys argent saltirewise (Papal coat of arms for Pope Nicholas V, 1447)
• Argent five martlets saltirewise sable on a chief azure three ducal crowns or (Bodley)
• Vert bordure or a caduceus argent and or and a cornucopia or with fruits and vegetables proper saltirewise (Coat of arms of Kharkiv, Ukraine)
• Vert bordure or a torch and a caduceus or saltirewise (Federal Customs Service of Russia)
• Argent two keys sable saltirewise under a cross pattée or (Lesser coat of arms of Riga, Latvia)
in supporters
• Papal coat of arms for Pope Innocent VIII with the Keys of Peter saltirewise (Wernigerode Armorial, c. 1490)
• Royal Coat of Arms of Spain (1700–1761)
• Coat of arms of Spain (1874–1931)
• Coat of arms of the House of Braganza.
other
• Coat of arms of Kaliningrad
• Coat of arms of Barbados with Sugar Canes held saltirewise.
• Vatican City's flag (Flag of Vatican City)
• Saint Alban's flag (13th century)
• Naval flag of the Kingdom of Sicily (after Guillem Soler c. 1380), inheriting the per saltire division from the royal coat of arms.

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