diff --git a/src/System.Runtime.Extensions/src/System/AppDomain.cs b/src/Common/src/CoreLib/System/AppDomain.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/AppDomain.cs
rename to src/Common/src/CoreLib/System/AppDomain.cs
diff --git a/src/System.Runtime.Extensions/src/System/AppDomainSetup.cs b/src/Common/src/CoreLib/System/AppDomainSetup.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/AppDomainSetup.cs
rename to src/Common/src/CoreLib/System/AppDomainSetup.cs
diff --git a/src/System.Runtime.Extensions/src/System/CannotUnloadAppDomainException.cs b/src/Common/src/CoreLib/System/CannotUnloadAppDomainException.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/CannotUnloadAppDomainException.cs
rename to src/Common/src/CoreLib/System/CannotUnloadAppDomainException.cs
diff --git a/src/System.Runtime.Extensions/src/System/Collections/ArrayList.cs b/src/Common/src/CoreLib/System/Collections/ArrayList.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Collections/ArrayList.cs
rename to src/Common/src/CoreLib/System/Collections/ArrayList.cs
diff --git a/src/System.Threading.Thread/src/System/LocalDataStoreSlot.cs b/src/Common/src/CoreLib/System/LocalDataStoreSlot.cs
similarity index 100%
rename from src/System.Threading.Thread/src/System/LocalDataStoreSlot.cs
rename to src/Common/src/CoreLib/System/LocalDataStoreSlot.cs
diff --git a/src/System.Runtime.Extensions/src/System/Security/IPermission.cs b/src/Common/src/CoreLib/System/Security/IPermission.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Security/IPermission.cs
rename to src/Common/src/CoreLib/System/Security/IPermission.cs
diff --git a/src/System.Runtime.Extensions/src/System/Security/ISecurityEncodable.cs b/src/Common/src/CoreLib/System/Security/ISecurityEncodable.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Security/ISecurityEncodable.cs
rename to src/Common/src/CoreLib/System/Security/ISecurityEncodable.cs
diff --git a/src/System.Runtime.Extensions/src/System/Security/IStackWalk.cs b/src/Common/src/CoreLib/System/Security/IStackWalk.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Security/IStackWalk.cs
rename to src/Common/src/CoreLib/System/Security/IStackWalk.cs
diff --git a/src/System.Runtime.Extensions/src/System/Security/PermissionSet.cs b/src/Common/src/CoreLib/System/Security/PermissionSet.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Security/PermissionSet.cs
rename to src/Common/src/CoreLib/System/Security/PermissionSet.cs
diff --git a/src/System.Runtime.Extensions/src/System/Security/Permissions/PermissionState.cs b/src/Common/src/CoreLib/System/Security/Permissions/PermissionState.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Security/Permissions/PermissionState.cs
rename to src/Common/src/CoreLib/System/Security/Permissions/PermissionState.cs
diff --git a/src/System.Security.Principal/src/System/Security/Principal/IIdentity.cs b/src/Common/src/CoreLib/System/Security/Principal/IIdentity.cs
similarity index 100%
rename from src/System.Security.Principal/src/System/Security/Principal/IIdentity.cs
rename to src/Common/src/CoreLib/System/Security/Principal/IIdentity.cs
diff --git a/src/System.Security.Principal/src/System/Security/Principal/IPrincipal.cs b/src/Common/src/CoreLib/System/Security/Principal/IPrincipal.cs
similarity index 100%
rename from src/System.Security.Principal/src/System/Security/Principal/IPrincipal.cs
rename to src/Common/src/CoreLib/System/Security/Principal/IPrincipal.cs
diff --git a/src/System.Security.Principal/src/System/Security/Principal/PrincipalPolicy.cs b/src/Common/src/CoreLib/System/Security/Principal/PrincipalPolicy.cs
similarity index 100%
rename from src/System.Security.Principal/src/System/Security/Principal/PrincipalPolicy.cs
rename to src/Common/src/CoreLib/System/Security/Principal/PrincipalPolicy.cs
diff --git a/src/System.Runtime.Extensions/src/System/Security/SecurityElement.cs b/src/Common/src/CoreLib/System/Security/SecurityElement.cs
similarity index 100%
rename from src/System.Runtime.Extensions/src/System/Security/SecurityElement.cs
rename to src/Common/src/CoreLib/System/Security/SecurityElement.cs
diff --git a/src/System.Threading.Thread/src/System/Threading/CompressedStack.cs b/src/Common/src/CoreLib/System/Threading/CompressedStack.cs
similarity index 100%
rename from src/System.Threading.Thread/src/System/Threading/CompressedStack.cs
rename to src/Common/src/CoreLib/System/Threading/CompressedStack.cs
diff --git a/src/System.Threading.Thread/src/System/Threading/Thread.Unix.cs b/src/Common/src/CoreLib/System/Threading/Thread.Unix.cs
similarity index 100%
rename from src/System.Threading.Thread/src/System/Threading/Thread.Unix.cs
rename to src/Common/src/CoreLib/System/Threading/Thread.Unix.cs
diff --git a/src/System.Threading.Thread/src/System/Threading/Thread.Windows.cs b/src/Common/src/CoreLib/System/Threading/Thread.Windows.cs
similarity index 100%
rename from src/System.Threading.Thread/src/System/Threading/Thread.Windows.cs
rename to src/Common/src/CoreLib/System/Threading/Thread.Windows.cs
diff --git a/src/System.Threading.Thread/src/System/Threading/Thread.cs b/src/Common/src/CoreLib/System/Threading/Thread.cs
similarity index 100%
rename from src/System.Threading.Thread/src/System/Threading/Thread.cs
rename to src/Common/src/CoreLib/System/Threading/Thread.cs
diff --git a/src/System.Runtime.Extensions/src/System.Runtime.Extensions.csproj b/src/System.Runtime.Extensions/src/System.Runtime.Extensions.csproj
index 3645aaa5a380..4c91053d3b3a 100644
--- a/src/System.Runtime.Extensions/src/System.Runtime.Extensions.csproj
+++ b/src/System.Runtime.Extensions/src/System.Runtime.Extensions.csproj
@@ -10,11 +10,8 @@
     <Configurations>netcoreapp-Unix-Debug;netcoreapp-Unix-Release;netcoreapp-Windows_NT-Debug;netcoreapp-Windows_NT-Release;netcoreappaot-Windows_NT-Debug;netcoreappaot-Windows_NT-Release;uap-Windows_NT-Debug;uap-Windows_NT-Release;uapaot-Windows_NT-Debug;uapaot-Windows_NT-Release</Configurations>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="System\AppDomain.cs" />
-    <Compile Include="System\AppDomainSetup.cs" />
     <Compile Include="System\AppDomainUnloadedException.cs" />
     <Compile Include="System\ApplicationId.cs" />
-    <Compile Include="System\CannotUnloadAppDomainException.cs" />
     <Compile Include="System\CodeDom\Compiler\IndentedTextWriter.cs" />
     <Compile Include="System\Context.cs" />
     <Compile Include="System\Diagnostics\Stopwatch.cs" />
@@ -36,18 +33,41 @@
     <Compile Include="System\Runtime\Versioning\ResourceScope.cs" />
     <Compile Include="System\Runtime\Versioning\VersioningHelper.cs" />
     <Compile Include="System\StringNormalizationExtensions.cs" />
-    <Compile Include="System\Collections\ArrayList.cs" />
-    <Compile Include="System\Security\IPermission.cs" />
-    <Compile Include="System\Security\ISecurityEncodable.cs" />
-    <Compile Include="System\Security\IStackWalk.cs" />
-    <Compile Include="System\Security\SecurityElement.cs" />
     <Compile Include="System\Security\Permissions\CodeAccessSecurityAttribute.cs" />
-    <Compile Include="System\Security\Permissions\PermissionState.cs" />
     <Compile Include="System\Security\Permissions\SecurityAction.cs" />
     <Compile Include="System\Security\Permissions\SecurityAttribute.cs" />
     <Compile Include="System\Security\Permissions\SecurityPermissionAttribute.cs" />
     <Compile Include="System\Security\Permissions\SecurityPermissionFlag.cs" />
-    <Compile Include="System\Security\PermissionSet.cs" />
+    <Compile Include="$(CommonPath)\CoreLib\System\AppDomain.cs">
+      <Link>Common\CoreLib\System\AppDomain.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\AppDomainSetup.cs">
+      <Link>Common\CoreLib\System\AppDomainSetup.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\CannotUnloadAppDomainException.cs">
+      <Link>Common\CoreLib\System\CannotUnloadAppDomainException.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Collections\ArrayList.cs">
+      <Link>Common\CoreLib\System\Collections\ArrayList.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\IPermission.cs">
+      <Link>Common\CoreLib\System\Security\IPermission.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\ISecurityEncodable.cs">
+      <Link>Common\CoreLib\System\Security\ISecurityEncodable.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\IStackWalk.cs">
+      <Link>Common\CoreLib\System\Security\IStackWalk.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\SecurityElement.cs">
+      <Link>Common\CoreLib\System\Security\SecurityElement.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\Permissions\PermissionState.cs">
+      <Link>Common\CoreLib\System\Security\Permissions\PermissionState.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\PermissionSet.cs">
+      <Link>Common\CoreLib\System\Security\PermissionSet.cs</Link>
+    </Compile>
     <Compile Include="$(CommonPath)\CoreLib\System\IO\StreamHelpers.CopyValidation.cs">
       <Link>Common\CoreLib\System\IO\StreamHelpers.CopyValidation.cs</Link>
     </Compile>
diff --git a/src/System.Security.Permissions/src/System.Security.Permissions.csproj b/src/System.Security.Permissions/src/System.Security.Permissions.csproj
index 950392877bbb..a9de940dc6a5 100644
--- a/src/System.Security.Permissions/src/System.Security.Permissions.csproj
+++ b/src/System.Security.Permissions/src/System.Security.Permissions.csproj
@@ -178,9 +178,15 @@
     <Compile Include="System\Web\AspNetHostingPermissionLevel.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetGroup)' == 'netstandard'">
-    <Compile Include="..\..\System.Runtime.Extensions\src\System\Security\IStackWalk.cs" />
-    <Compile Include="..\..\System.Runtime.Extensions\src\System\Security\PermissionSet.cs" />
-    <Compile Include="..\..\System.Runtime.Extensions\src\System\Security\Permissions\PermissionState.cs" />
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\IStackWalk.cs">
+      <Link>Common\CoreLib\System\Security\IStackWalk.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\PermissionSet.cs">
+      <Link>Common\CoreLib\System\Security\PermissionSet.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\Permissions\PermissionState.cs">
+      <Link>Common\CoreLib\System\Security\Permissions\PermissionState.cs</Link>
+    </Compile>
   </ItemGroup>
   <ItemGroup Condition="'$(TargetsNetFx)' == 'true'">
     <Reference Include="mscorlib" />
diff --git a/src/System.Security.Principal/src/System.Security.Principal.csproj b/src/System.Security.Principal/src/System.Security.Principal.csproj
index 10afa52d2440..444d07596053 100644
--- a/src/System.Security.Principal/src/System.Security.Principal.csproj
+++ b/src/System.Security.Principal/src/System.Security.Principal.csproj
@@ -7,9 +7,15 @@
   </PropertyGroup>
   <!-- Default configurations to help VS understand the options -->
   <ItemGroup>
-    <Compile Include="System\Security\Principal\IIdentity.cs" />
-    <Compile Include="System\Security\Principal\IPrincipal.cs" />
-    <Compile Include="System\Security\Principal\PrincipalPolicy.cs" />
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\Principal\IIdentity.cs">
+      <Link>Common\CoreLib\System\Security\Principal\IIdentity.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\Principal\IPrincipal.cs">
+      <Link>Common\CoreLib\System\Security\Principal\IPrincipal.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Security\Principal\PrincipalPolicy.cs">
+      <Link>Common\CoreLib\System\Security\Principal\PrincipalPolicy.cs</Link>
+    </Compile>
     <Compile Include="System\Security\Principal\TokenImpersonationLevel.cs" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/System.Threading.Thread/src/System.Threading.Thread.csproj b/src/System.Threading.Thread/src/System.Threading.Thread.csproj
index 829fea834bfd..3c687b42e247 100644
--- a/src/System.Threading.Thread/src/System.Threading.Thread.csproj
+++ b/src/System.Threading.Thread/src/System.Threading.Thread.csproj
@@ -7,11 +7,21 @@
     <Configurations>netcoreapp-Unix-Debug;netcoreapp-Unix-Release;netcoreapp-Windows_NT-Debug;netcoreapp-Windows_NT-Release;netcoreappaot-Windows_NT-Debug;netcoreappaot-Windows_NT-Release;uap-Windows_NT-Debug;uap-Windows_NT-Release;uapaot-Windows_NT-Debug;uapaot-Windows_NT-Release</Configurations>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="System\LocalDataStoreSlot.cs" />
-    <Compile Include="System\Threading\CompressedStack.cs" />
-    <Compile Include="System\Threading\Thread.cs" />
-    <Compile Include="System\Threading\Thread.Unix.cs" Condition="'$(TargetsUnix)' == 'true'" />
-    <Compile Include="System\Threading\Thread.Windows.cs" Condition="'$(TargetsWindows)' == 'true'" />
+    <Compile Include="$(CommonPath)\CoreLib\System\LocalDataStoreSlot.cs">
+      <Link>Common\CoreLib\System\LocalDataStoreSlot.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Threading\CompressedStack.cs">
+      <Link>Common\CoreLib\System\Threading\CompressedStack.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Threading\Thread.cs">
+      <Link>Common\CoreLib\System\Threading\Thread.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Threading\Thread.Unix.cs" Condition="'$(TargetsUnix)' == 'true'">
+      <Link>Common\CoreLib\System\Threading\Thread.Unix.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Threading\Thread.Windows.cs" Condition="'$(TargetsWindows)' == 'true'">
+      <Link>Common\CoreLib\System\Threading\Thread.Windows.cs</Link>
+    </Compile>
     <Compile Include="System\Threading\ThreadExceptionEventArgs.cs" />
   </ItemGroup>
   <ItemGroup>