diff --git a/scripts/create_drc_samples.rb b/scripts/create_drc_samples.rb
index b8ea6665a..fbf37b8b5 100644
--- a/scripts/create_drc_samples.rb
+++ b/scripts/create_drc_samples.rb
@@ -102,7 +102,7 @@ def run_demo(gen, cmd, out)
 
   gen.produce(cell.shapes(l1), cell.shapes(l2))
 
-  view.zoom_box(RBA::DBox::new(-2.0, -1.0, 8.0, 9.0))
+  view.zoom_box(RBA::DBox::new(-2.0, -2.0, 8.0, 9.0))
   view.max_hier
 
   t = RBA::Text::new(cmd, -1500, 8500)
@@ -144,7 +144,7 @@ SCRIPT
   end
 
   view.update_content
-  view.save_image(res_path + "/" + img_path + "/" + out, 400, 400)
+  view.save_image(res_path + "/" + img_path + "/" + out, 500, 500)
 
   puts "---> written #{res_path}/#{img_path}/#{out}"
 
@@ -709,5 +709,36 @@ run_demo gen, "labels & input2", "drc_textpoly1.png"
 run_demo gen, "labels - input2", "drc_textpoly2.png"
 
 
+class Gen
+  def produce(s1, s2)
+    s1.insert(RBA::Polygon::new(RBA::Box::new(0, 0, 6000, 2000)))
+    s2.insert(RBA::Polygon::new(RBA::Box::new(3500, 3000, 6000, 4000)))
+    s2.insert(RBA::Polygon::new(RBA::Box::new(0, 5000, 2500, 7000)))
+    s2.insert(RBA::Polygon::new(RBA::Box::new(3500, 5000, 6000, 7000)))
+  end
+end
+
+gen = Gen::new
+
+run_demo gen, "input1.separation(input2, 3.5.um, projection, \n                  shielded)", "drc_shielded1.png"
+run_demo gen, "input1.separation(input2, 3.5.um, projection, \n                  transparent)", "drc_shielded2.png"
+
+
+class Gen
+  def produce(s1, s2)
+    s1.insert(RBA::Polygon::new(RBA::Box::new(0, 0, 2500, 2000)))
+    s1.insert(RBA::Polygon::new(RBA::Box::new(3500, 0, 6000, 2000)))
+    s2.insert(RBA::Polygon::new(RBA::Box::new(3500, 0, 6000, 2000)))
+    s2.insert(RBA::Polygon::new(RBA::Box::new(0, 5000, 2500, 7000)))
+    s2.insert(RBA::Polygon::new(RBA::Box::new(3500, 5000, 6000, 7000)))
+  end
+end
+
+gen = Gen::new
+
+run_demo gen, "input1.separation(input2, 3.5.um, projection, \n                  shielded)", "drc_shielded3.png"
+run_demo gen, "input1.separation(input2, 3.5.um, projection, \n                  transparent)", "drc_shielded4.png"
+
+
 QRCGenerator::instance.finish
 
diff --git a/scripts/klayoutrc_drc_samples b/scripts/klayoutrc_drc_samples
index e00122048..4bdf2fb62 100644
--- a/scripts/klayoutrc_drc_samples
+++ b/scripts/klayoutrc_drc_samples
@@ -102,7 +102,7 @@
  <grid-color>#404040</grid-color>
  <grid-micron>0.1</grid-micron>
  <grid-show-ruler>true</grid-show-ruler>
- <grid-style0>lines</grid-style0>
+ <grid-style0>invisible</grid-style0>
  <grid-style1>dots</grid-style1>
  <grid-style2>tenths-dotted-lines</grid-style2>
  <grid-visible>true</grid-visible>
diff --git a/src/drc/drc/built-in-macros/_drc_engine.rb b/src/drc/drc/built-in-macros/_drc_engine.rb
index c575b7577..ed44c0a24 100644
--- a/src/drc/drc/built-in-macros/_drc_engine.rb
+++ b/src/drc/drc/built-in-macros/_drc_engine.rb
@@ -83,6 +83,14 @@ module DRC
       DRCSizingMode::new(4)
     end
     
+    def shielded
+      DRCShielded::new(true)
+    end
+    
+    def transparent
+      DRCShielded::new(false)
+    end
+    
     def projection_limits(*args)
       DRCProjectionLimits::new(*args)
     end
diff --git a/src/drc/drc/built-in-macros/_drc_layer.rb b/src/drc/drc/built-in-macros/_drc_layer.rb
index 161d9f897..1c1b4ba49 100644
--- a/src/drc/drc/built-in-macros/_drc_layer.rb
+++ b/src/drc/drc/built-in-macros/_drc_layer.rb
@@ -2471,6 +2471,8 @@ CODE
     #   @li @b projection_limits(min, max) or projection_limits(min .. max) @/b:
     #         this option makes the check only consider edge pairs whose projected length on
     #         each other is more or equal than min and less than max @/li
+    #   @li @b transparent @/b: performs the check without shielding (polygon layers only) @/li
+    #   @li @b shielded @/b: performs the check with shielding (polygon layers only) @/li
     # @/ul
     #
     # Note that without the angle_limit, acute corners will always be reported, since two 
@@ -2508,6 +2510,18 @@ CODE
     #     @td @img(/images/drc_width4.png) @/td
     #   @/tr
     # @/table
+    #
+    # "shielding" is a concept where an internal or external distance is measured only 
+    # if the opposite edge is not blocked by other edges between. Shielded mode makes 
+    # a difference if very large distances are to be checked and the minimum distance
+    # is much smaller: in this case, a large distance violation may be blocked by features
+    # located between the edges which are checked. With shielding, large distance violations
+    # are not reported in this case. Shielding is also effective at zero distance which has
+    # an adverse effect: Consider a case, where one layer A is a subset of another layer B. If 
+    # you try to check the distance between features of B vs. A, you cannot use shielding, 
+    # because B features which are identical to A features will shield those entirely. 
+    #
+    # Shielding is enabled by default, but can be switched off with the "transparent" option.
     
     # %DRC%
     # @name space
@@ -2685,6 +2699,7 @@ CODE
         alim = nil
         whole_edges = false
         other = nil
+        shielded = nil
 
         n = 1
         args.each do |a|
@@ -2699,6 +2714,8 @@ CODE
           elsif a.is_a?(DRCProjectionLimits)
             minp = @engine._prep_value(a.min)
             maxp = @engine._prep_value(a.max)
+          elsif a.is_a?(DRCShielded)
+            shielded = a.value
           elsif a.is_a?(Float) || a.is_a?(1.class)
             value && raise("Value already specified")
             value = @engine._prep_value(a)
@@ -2711,6 +2728,15 @@ CODE
         if !value
           raise("#{f}: A check value must be specified")
         end
+
+        args = [ value, whole_edges, metrics, alim, minp, maxp ]
+        if shielded != nil
+          if self.data.is_a?(RBA::Region)
+            args << shielded
+          else 
+            raise("#{f}: shielding can only be used for polygon layers")
+          end
+        end
         
         border = (metrics == RBA::Region::Square ? value * 1.5 : value)
         
@@ -2718,13 +2744,13 @@ CODE
           if other
             raise("No other layer must be specified for single-layer checks (i.e. width)")
           end
-          DRCLayer::new(@engine, @engine._tcmd(self.data, border, RBA::EdgePairs, :#{f}_check, value, whole_edges, metrics, alim, minp, maxp))
+          DRCLayer::new(@engine, @engine._tcmd(self.data, border, RBA::EdgePairs, :#{f}_check, *args))
         else
           if !other
             raise("The other layer must be specified for two-layer checks (i.e. overlap)")
           end
           requires_same_type(other, "#{f}")
-          DRCLayer::new(@engine, @engine._tcmd(self.data, border, RBA::EdgePairs, :#{f}_check, other.data, value, whole_edges, metrics, alim, minp, maxp))
+          DRCLayer::new(@engine, @engine._tcmd(self.data, border, RBA::EdgePairs, :#{f}_check, other.data, *args))
         end
         
       end  
@@ -3177,6 +3203,10 @@ CODE
       @data
     end
 
+    def data=(d)
+      @data = d
+    end
+
     def requires_region(f)
       self.data.is_a?(RBA::Region) || raise("#{f}: Requires a polygon layer")
     end
diff --git a/src/drc/drc/built-in-macros/_drc_tags.rb b/src/drc/drc/built-in-macros/_drc_tags.rb
index 4cbe21533..30f460f2f 100644
--- a/src/drc/drc/built-in-macros/_drc_tags.rb
+++ b/src/drc/drc/built-in-macros/_drc_tags.rb
@@ -126,5 +126,15 @@ module DRC
     end
   end
 
+  # A wrapper for specifying shielded mode
+  class DRCShielded
+    def initialize(f)
+      @value = f
+    end
+    def value
+      @value
+    end
+  end
+ 
 end
 
diff --git a/src/lay/lay/doc/about/drc_ref_layer.xml b/src/lay/lay/doc/about/drc_ref_layer.xml
index fe5f8f27c..96e0a164f 100644
--- a/src/lay/lay/doc/about/drc_ref_layer.xml
+++ b/src/lay/lay/doc/about/drc_ref_layer.xml
@@ -2176,6 +2176,8 @@ make the check only consider edges enclosing angles of less than 45 degree. </li
 <li><b>projection_limits(min, max) or projection_limits(min .. max) </b>:
 this option makes the check only consider edge pairs whose projected length on
 each other is more or equal than min and less than max </li>
+<li><b>transparent </b>: performs the check without shielding (polygon layers only) </li>
+<li><b>shielded </b>: performs the check with shielding (polygon layers only) </li>
 </ul>
 </p><p>
 Note that without the angle_limit, acute corners will always be reported, since two 
@@ -2213,6 +2215,18 @@ The following images show the effect of various forms of the width check:
 <td><img src="/images/drc_width4.png"/></td>
 </tr>
 </table>
+</p><p>
+"shielding" is a concept where an internal or external distance is measured only 
+if the opposite edge is not blocked by other edges between. Shielded mode makes 
+a difference if very large distances are to be checked and the minimum distance
+is much smaller: in this case, a large distance violation may be blocked by features
+located between the edges which are checked. With shielding, large distance violations
+are not reported in this case. Shielding is also effective at zero distance which has
+an adverse effect: Consider a case, where one layer A is a subset of another layer B. If 
+you try to check the distance between features of B vs. A, you cannot use shielding, 
+because B features which are indentical to A features will shield those entirely. 
+</p><p>
+Shielding is enabled by default, but can be switched off with the "transparent" option.
 </p>
 <a name="with_angle"/><h2>"with_angle" - Selects edges by their angle</h2>
 <keyword name="with_angle"/>
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diff --git a/src/lay/lay/doc/images/drc_xor1.png b/src/lay/lay/doc/images/drc_xor1.png
index 5ca89f97b..d33f65b84 100644
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diff --git a/src/lay/lay/doc/images/drc_xor2.png b/src/lay/lay/doc/images/drc_xor2.png
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diff --git a/src/lay/lay/doc/manual/drc_runsets.xml b/src/lay/lay/doc/manual/drc_runsets.xml
index 4af5bbddd..3b2927d78 100644
--- a/src/lay/lay/doc/manual/drc_runsets.xml
+++ b/src/lay/lay/doc/manual/drc_runsets.xml
@@ -70,6 +70,7 @@
 
 
   <h2>Including other files</h2>
+  <keyword name="include"/>
 
   <p>
   The DRC script language is based on Ruby which delivers many native language
@@ -506,6 +507,8 @@ output(w, "width violations")</pre>
   </ul>
 
   <h2>Polygon and edge layers</h2>
+  <keyword name="Polygon layer"/>
+  <keyword name="Edge layer"/>
 
   <p>
   KLayout knows four layer types: polygon, edge, edge pair and text layers.
@@ -573,6 +576,7 @@ output(w, "width violations")</pre>
   </p>
 
   <h2>Text collections</h2>
+  <keyword name="Text collections"/>
 
   <p>
   Starting with version 0.27, KLayout offers support for text layers.
@@ -618,6 +622,8 @@ output(w, "width violations")</pre>
   </ul>
 
   <h2>Edge pairs and edge pair collections</h2>
+  <keyword name="Edge pairs"/>
+  <keyword name="Edge pair collections"/>
 
   <p>
   Edge pairs are objects consisting of two edges. Edge pairs are handy when discribing a DRC check violation,
@@ -641,6 +647,8 @@ output(w, "width violations")</pre>
 
 
   <h2>Raw and clean layer mode</h2>
+  <keyword name="Raw mode"/>
+  <keyword name="Clean mode"/>
 
   <p>
   KLayout's DRC engine supports two basic ways to interpret geometrical information on a layer:
@@ -711,7 +719,56 @@ overlaps = layer.size(0.2).raw.merged(2)</pre>
   </table>
 
 
+  <h2>Shielding</h2>
+  <keyword name="Shielding"/>
+
+  <p>
+  "Shielding" is a concept where DRC measurements do not "look through" layout features.
+  With shielding, a DRC violation is skipped when another feature would (fully) block
+  the violation marker's path. Shielding is available and enabled by default for the (internal or external)
+  distance-based DRC functions:
+  <a href="/about/drc_ref_layer.xml#width">width</a>,
+  <a href="/about/drc_ref_layer.xml#space">space</a>,
+  <a href="/about/drc_ref_layer.xml#separation">separation (sep)</a>,
+  <a href="/about/drc_ref_layer.xml#notch">notch</a>,
+  <a href="/about/drc_ref_layer.xml#isolated">isolated (iso)</a>,
+  <a href="/about/drc_ref_layer.xml#enclosure">enclosure (enc)</a> or
+  <a href="/about/drc_ref_layer.xml#overlap">overlap</a>.
+  Shielding is turned off using the "transparent" option or turned on using "shielded". The latter
+  is only for clarity, but is not required as shielding is enabled by default.
+  </p>
+
+  <p>
+  The following examples demonstrate the effect of shielding: in the right example, shielding is turned off.
+  Hence, the violation between the upper box on the right and the lower bar is no longer shielded by the
+  small bar between them and this additional violation is reported too.
+  </p>
+
+  <table>
+    <tr>
+      <td><img src="/images/drc_shielded1.png"/></td>
+      <td><img src="/images/drc_shielded2.png"/></td>
+    </tr>
+  </table>
+
+  <p>
+  Although shielding feels more natural, it can have an adverse effect as it is effective at zero
+  distance already. In the following example, the second layer is a subset of the first. When
+  testing the distance between second and first, the overlapping first layer shapes will block
+  the separation measurement in shielded mode. Hence, only transparent mode will render the 
+  actual distance violation. The bottom right blue box is not shielded by the overlaying red box:
+  </p>
+
+  <table>
+    <tr>
+      <td><img src="/images/drc_shielded3.png"/></td>
+      <td><img src="/images/drc_shielded4.png"/></td>
+    </tr>
+  </table>
+
+
   <h2>Logging and verbosity</h2>
+  <keyword name="Logging"/>
 
   <p>
   While the runset is executed, a log is written that lists the methods and their execution times.
@@ -752,6 +809,7 @@ overlaps = layer.size(0.2).raw.merged(2)</pre>
   
 
   <h2>The tiling option</h2>
+  <keyword name="Tiling"/>
 
   <p>
   Tiling is a method to reduce the memory requirements for an operation. For big layouts, pulling a whole layer
@@ -831,6 +889,8 @@ no_borders</pre>
   </p>
 
   <h2>Hierarchical mode</h2>
+  <keyword name="Hierarchical mode"/>
+  <keyword name="Deep"/>
 
   <p>
   Alternatively to the tiling option, hierarchical mode is available. In hierarchical
diff --git a/src/lay/lay/layDRCLVSHelpResources.qrc b/src/lay/lay/layDRCLVSHelpResources.qrc
index 39a37e95b..e6f2f319e 100644
--- a/src/lay/lay/layDRCLVSHelpResources.qrc
+++ b/src/lay/lay/layDRCLVSHelpResources.qrc
@@ -95,5 +95,9 @@
   <file alias="drc_texts2.png">doc/images/drc_texts2.png</file>
   <file alias="drc_textpoly1.png">doc/images/drc_textpoly1.png</file>
   <file alias="drc_textpoly2.png">doc/images/drc_textpoly2.png</file>
+  <file alias="drc_shielded1.png">doc/images/drc_shielded1.png</file>
+  <file alias="drc_shielded2.png">doc/images/drc_shielded2.png</file>
+  <file alias="drc_shielded3.png">doc/images/drc_shielded3.png</file>
+  <file alias="drc_shielded4.png">doc/images/drc_shielded4.png</file>
  </qresource>
 </RCC>