Fill Hole (Vertices)

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

Fill Hole Options

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

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