There are two types of these poles, push in and put over. The first pole I had was called a "margin" put over poles, they are usually a max size of 8 metres(Browning) and are designed to take a fish "hit" of 18lbs which means they have some give in them.The majority of the bigger poles are push/put in. This means you put the next section inside the base of smaller pole. A put over pole is larger than the thinner section and you push the bigger section over tha smaller base by putting it over the outside of the smaller pole. Its difficult to explain unless you actually see the both types, then the penny drops.
Put overs are not usually very long, you would not use the three sections on the left of the picture as they are too thin.
The bottom (larger) sections of a put over pole are usually strong so if you later want to go higher you can cross match a put in pole into the base section of a put over.
Yes it will work if someone gives you a second hand one for say £20-40 and it will be a short but strong pole. But the top sections you use as with all poles are the weak point thats why I make the reccomendations in the diy topic that I do, it will save you time and money.
Its to do with the type of fishing, they are designed for fishing in the "margins" i.e. near the banks so that you can yank the fish out. The longer poles 16m are designed for going out further possibly to the other bank and shipping the pole in horizontally by removing the sections as you go. The line is only about 1-1.5m and attatched to the end section of the pole.
Blimey gone on for a bit and I am not even a fisherman.