Layers Sheet provides an editable table of Layer properties. Layers can be used to separate a Surface into multiple parts. Layers can be organized with regards to object types, system segments, or any other criteria. The Default Layer always remains, but other Layers may be created or removed using Add and Delete. Layers may be selected directly from the list. Up and Down change the position of a Layer in the list only (Layers are not stacked, so this does not affect Tab Order or visual overlapping). All objects in a given Layer can be selected with Select. Added Layers may be given a custom Name. View turns on/off visibility of a Layer in the Surface. NOTE: Objects cannot be selected when the current Layer is invisible. Lock prevents a Layer from being changed or selected. Lock and View may also be accessed by double-clicking on the corresponding icons within the list.