is 防 actually used for defense or did my app lie to me

ok so I learned 防 as PREVENT or defend like in waterproof things or maybe 防犯... wait is that crime prevention?? anyway i saw it on this weird sign at a station and i swear it looked like they used it for like crossing a bridge or passing something over to someone (is that 渡す??) and now im so confused. like does it actually mean defend in real life or did my vocab app just make it up. wait what was my question again l