Fill in (remove) a hole in a solid with the Sketch, Extrude and Combine/Merge tools. See two more ways here.
Drafting, Modeling and 3D Printing with Lydia Sloan Cline
Hand drafting for Interior Design, SketchUp, Autodesk 123D and MakerBot
Fill in (remove) a hole in a solid with the Sketch, Extrude and Combine/Merge tools. See two more ways here.