Layers are a very useful part of SketchUp, and they can make your life a lot easier. Here's how you can add a new layer in Sketchup and how you can move entities to different layers.
Adding a new layer
Follow these steps to add a layer to your SketchUp file:
Choose Window→Layers.
The Layers dialog box opens.
Click the Add Layer button to add a new layer to the Layers list.
If you want, you can double-click your new layer to rename it.
Another, slightly trickier, way to add a new layer to your model is to type a new layer name into the Layer field in the Entity Info dialog box, and then press Enter. (Find the Entity Info dialog box by choosing Window→Entity Info.)
This both creates a new layer with that name and moves whatever geometry is currently selected onto it. Save this particular time-saver for when you’re more experienced — nothing about Layers is as straightforward as it seems.
Moving entities to a different layer
Moving things from one layer to another involves using the Entity Info dialog box. Follow these steps to move an entity (an edge, face, group, or component) to a different layer:
Select the entity or entities you want to move to another layer.
Move only groups and components to other layers.
Choose Window→Entity Info.
The Entity Info dialog box opens. You can also open it by right-clicking your selected entities and choosing Entity Info from the context menu.
In the Entity Info dialog box, choose a layer from the Layer drop-down list.
Your selected entities are now on the layer you chose from the list.