A cross-dyke is a substantial linear earthwork, typically between 0.20 and 1km long comprising one or more ditches arranged beside and parallel to one or more banks, which runs across an upland ridge or across the neck of a spur. Univallate examples generally have a narrow flat bottomed ditch while multivallate examples have a ditch which is a V-shaped in cross-section. Cross-dykes are recognised as earthworks or as cropmarks on aerial photographs, or as a combination of both. Other components which may be present are trackways at the end or ends of the dykes.
Cross-dykes may be confused with other linear earthworks, particularly the dykes of oppida and linear boundaries which although similar in form, do not, however, have the same distinctive location and in the case of the latter are usually longer than cross-dykes, averaging over 1 km.
Specifically excluded here are pit alignments and frontier works.
Construction of cross-dykes, as revealed by excavation and by anology with associated monuments, appears to span a millenium from the Middle Bronze Age, though they may have been reused later. Superficially similar dykes may have been built for widely different reasons. Current interpretation prefers their use as territorial limits, and/ or as internal boundaries and land allotment within communities, although they were once seen rather as trackways, cattle droveways or defensive earthworks.