MKM Pottery Tools

I need some help here.  No matter what I do, I cannot join the nodes from two different closed shapes.  What I would like to do is break the curve between two nodes on each shape, and then join the ends of each curve together to form a single larger shape.  For instance, two separately drawn ovals joined to become one larger shape.  Merge does not seem to work, nor does simply breaking the curve between two nodes on each shape, and then rejoining the nodes from the separate shapes.  This is something I need to do all the time and I have  not been able to figure out a way to do this.    Thanks,  Rick