A markup layer is created from a normal layer, either by right-clicking the layer name on the layer tabs, or in the Drawings Hierarchy of the Impact Explorer. It is simply a new layer containing a layer insert of the original layer. Certain tools, such as Plot tool and Layer properties, are disabled for this type of layer.
Certain Diemaking tools (Dieboard Creator, Rotary Dieboard Creator, Rubber Creator, Blanker Creator, Matrix Creator and Stripper Creator) can all be run on a locked layer. If this happens, the tool will offer to create a Markup layer for that tool. This allows several people to simultaneously use different diemaking tools on the same project.