diff --git a/api/src/main/java/ai/djl/nn/convolutional/Conv2d.java b/api/src/main/java/ai/djl/nn/convolutional/Conv2d.java
index c68222cc119..4f5723a1d13 100644
--- a/api/src/main/java/ai/djl/nn/convolutional/Conv2d.java
+++ b/api/src/main/java/ai/djl/nn/convolutional/Conv2d.java
@@ -61,7 +61,7 @@ public class Conv2d extends Convolution {
     private static final String STRING_LAYOUT = "NCHW";
     private static final int NUM_DIMENSIONS = 4;
 
-    Conv2d(Builder builder) {
+    protected Conv2d(Builder builder) {
         super(builder);
     }
 
@@ -201,10 +201,10 @@ public static Builder builder() {
     }
 
     /** The Builder to construct a {@link Conv2d} type of {@link Block}. */
-    public static final class Builder extends ConvolutionBuilder<Builder> {
+    public static class Builder extends ConvolutionBuilder<Builder> {
 
         /** Creates a builder that can build a {@link Conv2d} block. */
-        Builder() {
+        protected Builder() {
             stride = new Shape(1, 1);
             padding = new Shape(0, 0);
             dilation = new Shape(1, 1);
diff --git a/api/src/main/java/ai/djl/nn/core/Linear.java b/api/src/main/java/ai/djl/nn/core/Linear.java
index 21e7941aed9..5524d6d10e3 100644
--- a/api/src/main/java/ai/djl/nn/core/Linear.java
+++ b/api/src/main/java/ai/djl/nn/core/Linear.java
@@ -64,7 +64,7 @@ public class Linear extends AbstractBlock {
     private Parameter weight;
     private Parameter bias;
 
-    Linear(Builder builder) {
+    protected Linear(Builder builder) {
         super(VERSION);
         units = builder.units;
         weight =
@@ -202,12 +202,12 @@ public static Builder builder() {
     }
 
     /** The Builder to construct a {@link Linear} type of {@link Block}. */
-    public static final class Builder {
+    public static class Builder {
 
-        private long units;
+        protected long units;
         private boolean bias = true;
 
-        Builder() {}
+        protected Builder() {}
 
         /**
          * Sets the number of output channels.
diff --git a/api/src/main/java/ai/djl/nn/norm/LayerNorm.java b/api/src/main/java/ai/djl/nn/norm/LayerNorm.java
index 7e7da567090..43ebd85b822 100644
--- a/api/src/main/java/ai/djl/nn/norm/LayerNorm.java
+++ b/api/src/main/java/ai/djl/nn/norm/LayerNorm.java
@@ -57,16 +57,16 @@
  */
 public class LayerNorm extends AbstractBlock {
 
-    private float epsilon;
-    private Shape normalizedShape;
+    protected float epsilon;
+    protected Shape normalizedShape;
 
-    private boolean center;
-    private boolean scale;
-    private int[] axis;
-    private Parameter gamma;
-    private Parameter beta;
+    protected boolean center;
+    protected boolean scale;
+    protected int[] axis;
+    protected Parameter gamma;
+    protected Parameter beta;
 
-    LayerNorm(Builder builder) {
+    protected LayerNorm(Builder builder) {
         epsilon = builder.epsilon;
         scale = builder.scale;
         center = builder.center;
@@ -186,7 +186,7 @@ public static final class Builder {
         private boolean center = true;
         private int[] axis;
 
-        Builder() {}
+        protected Builder() {}
 
         /**
          * List the axis over which the mean and variance will be calculated (alternative to