Wall layer: edit your current Layer Key Style and provide a different layer name for the WALL key. Better still, make a copy, edit the copy and then set the copy current. Unless you know you will never need the out-of-the-box settings and will never share your drawings with anyone else, I always recommend making customizations to ADT styles using a different name. That way there is no potential for the out-of-the-box version overwriting your customized version.
Walls can be drawn with hatched infills. Whether an infill displays depends upon the display settings in your current Display Configuration and your current view direction. The out-of-the-box wall styles use Material Definitions to avoid having style-level display overrides on all wall styles [as well as to provide one place to set how one material should be displayed, which can then be used in many styles]. For starters, assuming you are starting with one of the out-of-the-box ADT templates and using out-of-the-box wall styles, try setting the Presentation Display Configuration current and looking at walls that are cut by the cut plane in plan [Top view direction]. Then look at the High Detail Display Configuration.
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David Koch
Autodesk Discussion Group Facilitator