Also known as the Finnigirt Dyke, it has vanished in places at the southern end, although the ruins are clearly visible along much of the uninhabited north of the island, where it is a conspicuous feature of the landscape.

[13][14] Originally 1 metre (3 ft) wide it begins at the north shore by the cliffs of Muckle Funziegord Geo ("big Finns' dyke gully"), crosses an RSPB reserve to the west of Vord Hill, then vanishes near the enclosure of Whilsa Pund.

It reappears at the southern shore of Skutes Water, and is particularly well-preserved between Riggin of Setter and Rivs Dale, but its line is then lost again as it skirts the settlement of Houbie.

It may have crossed an area known as Vallahamars by the ruins of a later broch reaching the south coast of Fetlar near Stack of Billaclett, although local tradition asserts that it ended at the edge of the cliffs of Clemmels Geos (HU620905).

The remains of various structures lie within it and on the west side there is a shallow bay that forms an enclosure approximately 15 square metres (161 sq ft) in area.

Haswell-Smith (2004) speculatively implies a Mesolithic provenance[8] and a Bronze Age date has also been mentioned[11] although the Neolithic is quoted by some authoritative sources.

In historic times it acted as a boundary marker or hagri, but its huge scale is difficult to reconcile with the available prehistoric human resources.

[8][11] By contrast, "fealie dykes" were made of turf such as the nearby example at Burn of Feal less than 0.5 kilometres (550 yd) east of the line of the Funzie Girt south of Skutes Water.

[15][19] A strip of land 1 kilometre (0.62 mi) wide that ran along the dyke's eastern side was once known as "Houbie", now the name of Fetlar's principal settlement.

The notification to Sir Harold Stanley Nicolson of Brough Lodge, Fetlar states that the protected area is "2000 yards or thereby" (i.e. about 1,828 metres) in extent.

Fivl means "troll" (or "trow" in Shetland dialect), suggesting that there was a belief at one time that the dyke had been constructed by these mythical creatures.