Start with a Clove Hitch around both poles. Wrap six or eight turns around the two poles. Finish with another Clove Hitch. Two Round Lashings can be used to make a longer pole.
Use: The Round Lashing is similar to the one described by Ashley for scaffolding (ABOK # 2103, p 342) It is used to lash two parallel spars together to make a longer one.
Increased Security: Many descriptions describe the difficulty of making the lashing tight enough to be secure. A common recommendation is to hammer two wedges between the poles, one above and one below the lashing. This tightens the lashing and makes it more secure.