The H-bit means the following:

• It indicates whether the element is a solid or a hole for closed element types as shape, complex shape, ellipse, cone, B-spline surface header, and closed B-spline curve header:
  • false is Solid
  • true is Hole
• For a cell header if the H-bit is
  • false = Header for a cell
  • true = Header for an orphan cell
• For a a line:
  • false = Line segment
  • true = Infinite-length line
• For a point string element:
  • false = Continuous
  • true = Disjoint

The H-bit has no meaning in other elements.