Tutorial 3dsMax -- Cap Holes Modifier
The Cap Holes modifier builds faces in the holes in a mesh object. A hole is defined as a loop of edges, each of which has only one face. The modifier works best for filling planar holes, but can do a reasonable job with non-planar holes as well.
Note: This modifier can cap holes in a sub-object selection passed up the stack. It caps any part of the hole that's adjacent to, or within the selected geometry, whether vertex, edge, or face.
Sometimes completely unknown, the modifiers are very useful during the normal workflow of 3dsMax. These are old videos created with 3dsMax2010 but the modifiers are equal to the latest versions