SketchUp files contain layers, which you can manage in the Layers Registry. Here you can manage which layers are visible, which are used for floor detection, and

To manage layers:

1. Select Tools > Layer Registry.

   The registry is displayed.

   
   
   
2. From the 'Scene' drop-down menu, select 'All' to display all layers in your model, or choose a specific scene to show only layers associated with it.
3. Check or uncheck 'Visible' to show or hide a layer in the workspace.
4. Check or uncheck 'Floor Detection' to use or exclude a layer from being used to detect a floor level.
5. Click Close when you have finished.