diff --git a/applications/test/vectorTools/Test-vectorTools.C b/applications/test/vectorTools/Test-vectorTools.C
index 85d18ed989..24f17b5660 100644
--- a/applications/test/vectorTools/Test-vectorTools.C
+++ b/applications/test/vectorTools/Test-vectorTools.C
@@ -31,8 +31,9 @@ void test(const vector& a, const vector& b, const scalar tolerance)
 
 int main()
 {
-    vector a(1.0, 1.0, 1.0);
-    vector b(2.0, 2.0, 2.0);
+    vector a(vector::uniform(1));
+    vector b;
+    b.fill(2);
 
     test(a, b, 0.0);
     test(a, b, VSMALL);
@@ -67,5 +68,9 @@ int main()
     test(a, b, 1e-3);
     test(a, b, 1e-1);
 
+    Info<< "\nEnd\n" << nl;
+
     return 0;
 }
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
diff --git a/src/OpenFOAM/compat/Scalar.C b/src/OpenFOAM/compat/Scalar.C
new file mode 100644
index 0000000000..7cec1b4541
--- /dev/null
+++ b/src/OpenFOAM/compat/Scalar.C
@@ -0,0 +1 @@
+#warning File removed - left for old dependency check only
diff --git a/src/OpenFOAM/compat/Scalar.H b/src/OpenFOAM/compat/Scalar.H
new file mode 100644
index 0000000000..7cec1b4541
--- /dev/null
+++ b/src/OpenFOAM/compat/Scalar.H
@@ -0,0 +1 @@
+#warning File removed - left for old dependency check only
diff --git a/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.C b/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.C
index a50db2bad3..9ce62af909 100644
--- a/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.C
+++ b/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.C
@@ -31,12 +31,12 @@ License
 #include "parsing.H"
 #include "IOstreams.H"
 
-#include <cstdlib>
+#include <cstdlib>  // For string -> floating point conversions
 #include <sstream>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-// Scalar.C is used for template-like substitution
+// scalarImpl.C is used for template-like substitution (but using macros)
 
 #define Scalar doubleScalar
 #define ScalarVGREAT doubleScalarVGREAT
@@ -47,7 +47,9 @@ License
 // Convert using larger representation to properly capture underflow
 #define ScalarConvert ::strtold
 
-#include "Scalar.C"
+#define Foam_use_scalarImpl_code
+#include "scalarImpl.C"
+#undef Foam_use_scalarImpl_code
 
 #undef Scalar
 #undef ScalarVGREAT
diff --git a/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.H b/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.H
index fba14df589..1ecae4dbac 100644
--- a/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.H
+++ b/src/OpenFOAM/primitives/Scalar/doubleScalar/doubleScalar.H
@@ -144,7 +144,11 @@ inline Scalar func(const Scalar s)                              \
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-#include "Scalar.H"
+// scalarImpl.H is used for template-like substitution (but using macros)
+
+#define Foam_use_scalarImpl_header
+#include "scalarImpl.H"
+#undef Foam_use_scalarImpl_header
 
 #undef Scalar
 #undef ScalarVGREAT
diff --git a/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.C b/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.C
index 8f36aee0da..4bf5d83478 100644
--- a/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.C
+++ b/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.C
@@ -31,11 +31,12 @@ License
 #include "parsing.H"
 #include "IOstreams.H"
 
+#include <cstdlib>  // For string -> floating point conversions
 #include <sstream>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-// Scalar.C is used for template-like substitution
+// scalarImpl.C is used for template-like substitution (but using macros)
 
 #define Scalar floatScalar
 #define ScalarVGREAT floatScalarVGREAT
@@ -46,7 +47,9 @@ License
 // Convert using larger representation to properly capture underflow
 #define ScalarConvert ::strtod
 
-#include "Scalar.C"
+#define Foam_use_scalarImpl_code
+#include "scalarImpl.C"
+#undef Foam_use_scalarImpl_code
 
 #undef Scalar
 #undef ScalarVGREAT
diff --git a/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.H b/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.H
index 8d041a0111..d8024a2315 100644
--- a/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.H
+++ b/src/OpenFOAM/primitives/Scalar/floatScalar/floatScalar.H
@@ -157,7 +157,11 @@ inline Scalar func(const Scalar s)                              \
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-#include "Scalar.H"
+// scalarImpl.H is used for template-like substitution (but using macros)
+
+#define Foam_use_scalarImpl_header
+#include "scalarImpl.H"
+#undef Foam_use_scalarImpl_header
 
 #undef Scalar
 #undef ScalarVGREAT
diff --git a/src/OpenFOAM/primitives/Scalar/Scalar.C b/src/OpenFOAM/primitives/Scalar/scalarImpl.C
similarity index 97%
rename from src/OpenFOAM/primitives/Scalar/Scalar.C
rename to src/OpenFOAM/primitives/Scalar/scalarImpl.C
index bba2f8fd12..37ebc9e840 100644
--- a/src/OpenFOAM/primitives/Scalar/Scalar.C
+++ b/src/OpenFOAM/primitives/Scalar/scalarImpl.C
@@ -26,6 +26,11 @@ License
 
 \*---------------------------------------------------------------------------*/
 
+// Could also check if 'Scalar' is defined...
+#ifndef Foam_use_scalarImpl_code
+#error  "scalarImpl.C" is only to be included internally
+#endif
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 namespace Foam
diff --git a/src/OpenFOAM/primitives/Scalar/Scalar.H b/src/OpenFOAM/primitives/Scalar/scalarImpl.H
similarity index 98%
rename from src/OpenFOAM/primitives/Scalar/Scalar.H
rename to src/OpenFOAM/primitives/Scalar/scalarImpl.H
index fbd89c4308..2517aa0aef 100644
--- a/src/OpenFOAM/primitives/Scalar/Scalar.H
+++ b/src/OpenFOAM/primitives/Scalar/scalarImpl.H
@@ -51,10 +51,16 @@ Note
     \endcode
 
 SourceFiles
-    Scalar.C
+    scalarImpl.C
 
 \*---------------------------------------------------------------------------*/
 
+// Could also check if 'Scalar' is defined...
+#ifndef Foam_use_scalarImpl_header
+#error  "scalarImpl.H" is only to be included internally
+#endif
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 namespace Foam
diff --git a/src/OpenFOAM/primitives/VectorSpace/VectorSpace.H b/src/OpenFOAM/primitives/VectorSpace/VectorSpace.H
index 814769e795..048f49bb40 100644
--- a/src/OpenFOAM/primitives/VectorSpace/VectorSpace.H
+++ b/src/OpenFOAM/primitives/VectorSpace/VectorSpace.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2021 OpenCFD Ltd.
+    Copyright (C) 2019-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -191,6 +191,9 @@ public:
         //- Return pointer to the first data element
         inline Cmpt* data() noexcept;
 
+        //- Assign all components to given value
+        inline void fill(const Cmpt& s);
+
         //- Return a VectorSpace with all elements = s
         inline static Form uniform(const Cmpt& s);
 
diff --git a/src/OpenFOAM/primitives/VectorSpace/VectorSpaceI.H b/src/OpenFOAM/primitives/VectorSpace/VectorSpaceI.H
index 812b369986..7f8bbd46dc 100644
--- a/src/OpenFOAM/primitives/VectorSpace/VectorSpaceI.H
+++ b/src/OpenFOAM/primitives/VectorSpace/VectorSpaceI.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2022 OpenCFD Ltd.
+    Copyright (C) 2019-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -160,6 +160,13 @@ inline void Foam::VectorSpace<Form, Cmpt, Ncmpts>::replace
 }
 
 
+template<class Form, class Cmpt, Foam::direction Ncmpts>
+inline void Foam::VectorSpace<Form, Cmpt, Ncmpts>::fill(const Cmpt& s)
+{
+    VectorSpaceOps<Ncmpts,0>::eqOpS(*this, s, eqOp<Cmpt>());
+}
+
+
 template<class Form, class Cmpt, Foam::direction Ncmpts>
 inline Form Foam::VectorSpace<Form, Cmpt, Ncmpts>::uniform(const Cmpt& s)
 {