barrier

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