diff --git a/technology/freepdk45/tech/tech.py b/technology/freepdk45/tech/tech.py
index fcdb2c10..839a38af 100644
--- a/technology/freepdk45/tech/tech.py
+++ b/technology/freepdk45/tech/tech.py
@@ -7,10 +7,17 @@
 #
 import os
 from design_rules import *
+from module_type import *
 
 """
 File containing the process technology parameters for FreePDK 45nm.
 """
+# This uses the default classes to instantiate module from
+# '$OPENRAM_HOME/compiler/modules'.
+# Using tech_modules['cellname'] you can override each class by providing a custom
+# implementation in '$OPENRAM_TECHDIR/modules/'
+# For example: tech_modules['contact'] = 'contact_freepdk45'
+tech_modules = ModuleType()
 
 #GDS file info
 GDS = {}
diff --git a/technology/scn3me_subm/tech/tech.py b/technology/scn3me_subm/tech/tech.py
index 6fc68686..cb476df5 100755
--- a/technology/scn3me_subm/tech/tech.py
+++ b/technology/scn3me_subm/tech/tech.py
@@ -1,9 +1,16 @@
 import os
 from design_rules import *
+from module_type import *
 
 """
 File containing the process technology parameters for SCMOS 3me, subm, 180nm.
 """
+# This uses the default classes to instantiate module from
+# '$OPENRAM_HOME/compiler/modules'.
+# Using tech_modules['cellname'] you can override each class by providing a custom
+# implementation in '$OPENRAM_TECHDIR/modules/'
+# For example: tech_modules['contact'] = 'contact_scn3me'
+tech_modules = ModuleType()
 
 #GDS file info
 GDS={}
diff --git a/technology/scn4m_subm/tech/tech.py b/technology/scn4m_subm/tech/tech.py
index 3f42e8b3..d17a0927 100644
--- a/technology/scn4m_subm/tech/tech.py
+++ b/technology/scn4m_subm/tech/tech.py
@@ -7,10 +7,17 @@
 #
 import os
 from design_rules import *
+from module_type import *
 
 """
 File containing the process technology parameters for SCMOS 4m, 0.35um
 """
+# This uses the default classes to instantiate module from
+# '$OPENRAM_HOME/compiler/modules'.
+# Using tech_modules['cellname'] you can override each class by providing a custom
+# implementation in '$OPENRAM_TECHDIR/modules/'
+# For example: tech_modules['contact'] = 'contact_scn4m'
+tech_modules = ModuleType()
 
 #GDS file info
 GDS={}