A printed circuit board is made up of several “layers”. These include copper layers, mask and legend layers, drill files and more. Each layer is described by one (or sometimes two) image files, and normally a file describes only one layer. The Layer overview shows the filenames and layer names of the board. The check boxes for each layer may be used to view or hide the layer in the graphic display. The rectangle to the right of the check box shows the color used to display the layer in the Graphic Display. You can right-click on this rectangle to change the color.
The Route layer is automatically generated by adding contour objects (in the Contour pane).
The controls at the top of the Layer Overview may be used to specify the number of copper layers on the board. This is automatically increased if you link additional layers in the Files pane. However, if you want to reduce the number of copper layers, you must do so here.
For single layer boards, it is not possible to link a soldermask file to the non-copper side of the board. In the Board Specifications pane, the soldermask color for the non-copper side will be set to None. Changing this to another color will indicate that the board should have soldermask on the non-copper side.
You may right-click on the layer overview to quickly show only top layers, only bottom layers, all layers or no layers.