The most commonly used lashing for extending the length of a pole is the round lashing. The most common way this lashing is tied is with a clove hitch around both poles followed by eight to ten tight wraps that are flush together, and then ending with another clove hitch around both poles.
There are no frapping turns. The manner in which this lashing needs to be applied results in the poles being in a position where they are already tightly touching. Taking frapping turns between the parallel poles would only weaken the connection.
The objective is to combine the poles together to make a longer length that is as rigid as possible. So, connecting two poles in this fashion definitely requires a good overlap between them. It also requires two lashings, each tied tightly well near the ends of each pole where they overlap.
