Fill Hole (Edges)

The Fill Hole tool creates a new face that fills any holes that touch the selected edges.

Fill Hole Options

Enable the Fill Entire Hole option to fill the entire Mesh opening. This is the default.

If you disable this option, ProBuilder tries to build a Mesh between the selected open edges. For example, if you have a missing quad, you can select two adjacent edges in order to create a triangular polygon that covers half of the hole.