wall

bar, pale, paling

block, chain, clog, crimp, deterrent, drag, embarrassment, encumbrance, handicap, hindrance, hurdle, impediment, inhibition, interference, let, obstacle, obstruction, roadblock, stop, stumbling block, trammel

fetter, hobble, manacle, shackle(s)

constraint, curb, restraint, snag

buffer, bulwark, bumper, cushion, dam, fender, pad, rampart

arm, armament, munitions, weapon, weaponry

fastness, fort, fortress, palisade, stronghold