Dividing and Healing Geometry

Some tools speed up design dramatically by allowing you to perform modifications on existing geometry. For example, the Line Tool allows you to split faces and edges to create additional independent faces and edges. Simply divide the face or edge with another edge. This concept is similar to cutting a piece of wood in half and having two separate remaining pieces. The following image shows how two faces are created when dividing the face with a line. Notice the image on the left has one solid top face, while the image on the right has two independent faces when split with a line. Note that the dividing line does not cut through the model from top to bottom, but just cuts the top face in half.

The following image shows how the edges at each end of the face have been split to create additional edges. Note four edges bounding the face in the left image, while four edges bounding each of two faces in the image on the right (the middle edge being common to both top faces).  

If you remove the line that shared by the two faces in the image on the right, the two faces will be glued back together or healed back into one face. It is common in SketchUp to perform these dividing and healing operations to your model.