This command creates a solid model file (.MDL) by stitching
together a series of closed 3D polylines that form the ribs or
series of hoops for the solid.
Select rib polylines to process.
Select objects: pick the 3D polylines
Solid File To Write Select MDL file
Pulldown Menu Location: Solid
Keyboard Command: pl2solid
Prerequisite: closed 3D polylines