I added edge polylines before mirroring.
One segment can be mirrored 3 times in top view, for 2 cubed = 8 segments.
Two more mirrors in right view yields 2 power 5 = 32 segments.
Rotation copy of two 8 segments yields 48 total segments.
A solid can be created.


One segment consists of two parts separated by a straight line. Doing this trim enables a half
catenoid-like surface, with one square end, to be created.

- Brian