If your talking about the street sign poles that are fat and round then yes they slide good and you'll need two of them. Good luck at getting it out of the ground or sawing it. To acquire one you'll need...
1. Jackhammer (to bust up the concrete that is around it)
1. A saw
2. A friend to watch for cars
3. Darkness so no one sees you
good advice yo. in my opinion its just so risky. like i mean using a hack saw in pitch black and a risk of someone flipping shit out at you? just build one for 15 bucks or just look in some other threads. also if your talking about sliding medal street signs, go for it, just watchout for the holes