barrier brick fence Frontier stone stones stop wall appearance coloring colors colouring colours constructed dry-stone-hedge dry-stone-wall drystane-dyke fitted free-standing large light local-stone old patchwork perspectives random randomly-coursed rock-fence rocks rough rugged rural secure security shaped shapes sharp solid stone-fence stone-walled stonework strength strong sunlight sunshine surface surfaces texture textures uneven variations variety walled background pattern pebble pebbles rock tile divide dry drystane drystone dyke lichen boundary farm field historical meadow Pembrokeshire traditional wales welsh abstract ancient blurs church clouds cross decay elements grass rust sky