Replying to Rail build

I have 2 10' poles (one was from a swingset and the other was from an old skateboard rail my bro built. If they don't slide the same (not sure if they do or don't), is that a problem? also, should i do:

20' single barrel?
10' double?
10' spread double (like a foot between the 2 poles)?

Also, how do i secure them to whatever i mount them on? Liquid nails?
actual nails?
should i cut a groove out on the wood (if i mount it on wood) and just rest it in there?