Ключевые слова: abstract, backgrounds, barrier, border, boundary, cage, cars, chain, clouds, danger, distance, fence, frame, grating, horizon, iron, isolated, line, link, mesh, metal, metallic, net, netting, pattern, protection, railroad, railway, restriction, seamless, security, shape, sign, silhouette, sky, square, steel, symbol, territory, texture, train, transport, triangle, trucking, warning, wire, wires,