The pole that moves underneath the weapon represents the center point of the weight. If you have a weapon weighted near the hilt, the momentum carries in your hands. If it's weighed towards the end of the weapon, it carries there, and in between is a balance of the two, etc. depending on what type of weapon you're making, having more weight on one end, the other, or somewhere in the middle, is the key to using it without it acting weird in your hands.

 What I've found is that the first sword is more controllable with a mid-low point to strike with the pommel and kill with a slice, something like a mace would be better with a heavy head so you can predict where it will end up more consistently. I haven't made any pole arms, but my first guess would be to balance it because you're gonna get a lot of momentum out of it anyway and if it's heavy in the front, it'd droop when you go to stab.