Connecting two screws? I'm new to blender and I am looking for an easy way to connect two screws. Currently I have this double helix structure that I made by constructing two screws from circles:  
I am looking to connect one of the sides of the double helix like this:

I've tried making a tube using a bezier circle/path but can't find a way to attach it to the ends of the screw easy and seamlessly.
Move both the ends of the helix toward their common centre using proportional editing, then remove doubles and adjust with proportional editing.