Lofts or skins two or more separate closed Curves to create a surface.
The join closed curves process is similar to lofting bulkhead frames in boatbuilding. The curves' vertices must all be selected. The curves must not have loops or gaps. Any difference in the number of vertices of the first curve will be evenly distributed among the nearest corresponding vertices in the second curve. That is, a curve with 20 vertices can be smoothly lofted to a curve having only 10 vertices.
Before Joining Curves
After
Joining Curves