diff --git a/src/lay/lay/doc/about/index.xml b/src/lay/lay/doc/about/index.xml
index 71465e8ab..948703245 100644
--- a/src/lay/lay/doc/about/index.xml
+++ b/src/lay/lay/doc/about/index.xml
@@ -12,6 +12,7 @@
 
   <topics>
     <topic href="/about/layer_mapping.xml"/>
+    <topic href="/about/layer_specs.xml"/>
     <topic href="/about/transformations.xml"/>
     <topic href="/about/expressions.xml"/>
     <topic href="/about/variant_notation.xml"/>
diff --git a/src/lay/lay/doc/about/layer_specs.xml b/src/lay/lay/doc/about/layer_specs.xml
new file mode 100644
index 000000000..eb63bb9a7
--- /dev/null
+++ b/src/lay/lay/doc/about/layer_specs.xml
@@ -0,0 +1,104 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE language SYSTEM "klayout_doc.dtd">
+
+<doc>
+
+  <title>About Layer Specifications</title>
+
+  <p>
+  Layer specifications are used in various places, for example in layer mapping
+  files (<link href="/about/layer_mapping.xml"/>). 
+  Layer specifications are used inside the database to give a layer a name or 
+  a number/datatype pair or both. Layer specifications are the text representation
+  of <class_doc href="LayerInfo">LayerInfo</class_doc> objects.
+  </p>
+
+  <p>
+  Blanks within layer specifications are ignored and can be put between
+  the different components of the specification.
+  </p>
+
+  <p>
+  A simple number for the specification will indicate a layer with this layer number and a 
+  datatype of zero:
+  </p>
+
+  <pre>17</pre> 
+
+  <p>will give layer 17, datatype 0.
+  </p>
+
+  <p>
+  A number followed by a slash and another number will indicate a layer number 
+  and datatype:
+  </p>
+
+  <pre>17/5</pre> 
+
+  <p>
+  will give layer 17, datatype 5.
+  </p>
+
+  <p>
+  Layers can be named. Named layers are present in DXF, CIF or other formats
+  which don't use the GDS layer/datatype number scheme. Just giving a name 
+  will indicate such a layer:
+  </p>
+
+  <pre>METAL1</pre>
+
+  <p>
+  will give a named layer called "METAL1".
+  </p>
+
+  <p>
+  If you want to use a name that is a number, use quotes:
+  </p>
+
+  <pre>"17"</pre>
+
+  <p>
+  will give a named layer called "17".
+  </p>
+
+  <p>
+  If you want to use a name that includes blanks, put it into quotes
+  as well:
+  </p>
+
+  <pre>"METAL 1"</pre>
+
+  <p>
+  will give a named layer called "METAL 1" (however, such layer names are usually illegal).
+  </p>
+
+  <p>
+  Finally, a layer can have both a name and layer/datatype numbers.
+  In this case, add the layer/datatype number to the name in round
+  brackets:
+  </p>
+
+  <pre>METAL1 (17)</pre>
+
+  <p>
+  will give a layer named "METAL1" with layer 17 and datatype 0 and
+  </p>
+
+  <pre>METAL1 (17/5)</pre>
+
+  <p>
+  will give a layer named "METAL1" with layer 17 and datatype 5.
+  </p>
+
+  <h4>Layer specifications as targets</h4>
+
+  <p>
+  When used in a target context (e.g. for layer mapping), a layer specification
+  can use wildcards and relative layer/datatype specifications.
+  Using "*" instead of a layer or datatype number means to reuse the source 
+  layer or datatype number. Using "+x" or "-x" for layer or datatype number means
+  to add or subtract "x" from the source layer or datatype number.
+  </p>
+
+</doc>
+
diff --git a/src/lay/lay/layHelpResources.qrc b/src/lay/lay/layHelpResources.qrc
index 731ef64c8..e840931ef 100644
--- a/src/lay/lay/layHelpResources.qrc
+++ b/src/lay/lay/layHelpResources.qrc
@@ -21,6 +21,7 @@
         <file alias="ide_snapshot.png">doc/about/ide_snapshot.png</file>
         <file alias="index.xml">doc/about/index.xml</file>
         <file alias="layer_mapping.xml">doc/about/layer_mapping.xml</file>
+        <file alias="layer_specs.xml">doc/about/layer_specs.xml</file>
         <file alias="layer_sources.xml">doc/about/layer_sources.xml</file>
         <file alias="macro_editor.xml">doc/about/macro_editor.xml</file>
         <file alias="macro_in_menu.xml">doc/about/macro_in_menu.xml</file>
diff --git a/src/plugins/streamers/lefdef/lay_plugin/LEFDEFTechnologyComponentEditor.ui b/src/plugins/streamers/lefdef/lay_plugin/LEFDEFTechnologyComponentEditor.ui
index 65c1784f4..7ddb0871a 100644
--- a/src/plugins/streamers/lefdef/lay_plugin/LEFDEFTechnologyComponentEditor.ui
+++ b/src/plugins/streamers/lefdef/lay_plugin/LEFDEFTechnologyComponentEditor.ui
@@ -587,6 +587,16 @@
         </property>
        </widget>
       </item>
+      <item row="4" column="5" colspan="3">
+       <widget class="QLabel" name="help_label2">
+        <property name="text">
+         <string>&lt;html&gt;&lt;body&gt;(&lt;a href=&quot;int:/about/layer_specs.xml&quot;&gt;See here for the layer specification&lt;/a&gt;)&lt;/body&gt;&lt;/html&gt;</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>
diff --git a/src/plugins/streamers/lefdef/lay_plugin/layLEFDEFImportDialogs.cc b/src/plugins/streamers/lefdef/lay_plugin/layLEFDEFImportDialogs.cc
index 0cfded15b..868aca328 100644
--- a/src/plugins/streamers/lefdef/lay_plugin/layLEFDEFImportDialogs.cc
+++ b/src/plugins/streamers/lefdef/lay_plugin/layLEFDEFImportDialogs.cc
@@ -366,6 +366,7 @@ LEFDEFReaderOptionsEditor::LEFDEFReaderOptionsEditor (QWidget *parent)
   connect (browse_mapfile, SIGNAL (clicked ()), this, SLOT (browse_mapfile_clicked ()));
 
   lay::activate_help_links (help_label);
+  lay::activate_help_links (help_label2);
 }
 
 void