The constructed boundaries at Bosigran are in many cases fossilising the lines of earlier boundaries, lines of MBA, R-B or medieval date (see, for example, 94440, 94462, 94463, 94465). Several types of constructed boundary can be recognised - Cornish hedges, revetted lynchets (94475), turf banks (94477), stone-faced banks (94478), stone-faced stone walls ((4479), dry stone walls (94480), and single-stone walls (94481). These boundaries, like the lynchets and banks (94473 and 94472), can be valued according to the importance of the field system they fossilise. The type of modern boundary is of lesser importance, and most boundaries incorporate lynchets, usually by revetting them. When constructed boundaries are arranged in crude chronological order, amongst the earliest are usually some Cornish hedges, the traditional local boundary type, although, as is the case with traditions, some of the most recently constructed boundaries are also Cornish hedges. (This illustrates the futility of attempting to date a Zennor boundary on morphological grounds alone.) Cornish hedges have two tapering stone faces with cores of earth and small stones, often with a planted thorn hedge (a source of fuel and shelter) on top. They range from 0.9 to 1.5m high, from 1.0 to 1.5m wide at the base, 0.6 to 1.2m wide at the top. The earth fill encourages the growth of hedgerow plants on their faces as well as their tops. Walling styles vary but the lowest layers are normally of large stones laid flat as grounders. Several types of stonework are visible at Bosigran; some are carefully coursed, most are rubble built. The long axes of stones generally run into the hedge to give the faces greater strength. Where possible, no projections are left which could provide footholds for stock - these are intended to be stock-proof boundaries. The hedges require regular maintenance and throughout the field system there are signs of repairs and, in places, complete rebuilds of hedges. The lower courses and grounders of some Cornish hedges, however, will be of medieval, or even prehistoric, date.