rampart

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

barricade, barrier, fence, hedge, 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