Crack, Cranny, Crevasse, Crevice, Crimp, Cut, Dam, Defile, Dell, Ditch, Donga, Draw, Dugout, Earthwork, Embankment, Entrenchment, Excavation, Fault, Fence, Fissure, Flaw, Foxhole, Fracture, Furrow, Gallery, Gap, Gape, Gash, Gate, Gorge, Groin, Groove, Gulf, Gully, Gutter, Hole, Incision, Jam, Jetty, Joint, Kennel, Kloof, Leak, Logjam, Mine, Mole, Mound, Notch, Opening, Parallel, Parapet, Pass, Passage, Pleat, Portcullis, Rampart, Ravine, Rent, Rift, Rime, Roadblock, Rupture, Sap, Seam, Slit, Slot, Split, Trench, Trough, Tunnel, Valley, Void, Wadi, Wall, Weir, Work, Abyss, Aqueduct, Bank, Bar, Barrage, Barrier, Boom, Breach, Break, Breakwater, Buffer, Bulkhead, Bulwark, Bunker, Canal, Canyon, Cavity, Channel, Chap, Chasm, Check, Chimney, Chink, Cleft, Cofferdam, Col, Couloir