diff --git a/src/main/java/org/pasteque/coreutil/extra/ExtraBuilder.java b/src/main/java/org/pasteque/coreutil/extra/ExtraBuilder.java
index 4186882..f097f63 100644
--- a/src/main/java/org/pasteque/coreutil/extra/ExtraBuilder.java
+++ b/src/main/java/org/pasteque/coreutil/extra/ExtraBuilder.java
@@ -21,6 +21,8 @@ public final class ExtraBuilder
 
     /**
      * Create an empty builder to create an {@link ExtraObject}.
+     * It will be already pointing to the root object and values can be added
+     * to it.
      */
     public ExtraBuilder() {
         this.path = new ArrayList<ExtraData>();
@@ -198,6 +200,28 @@ public final class ExtraBuilder
         }
     }
 
+    /**
+     * Add a value to the current array.
+     * @param value The value to add.
+     * @throws IllegalStateException When not currently building an array.
+     * @throws IllegalArgumentException When not building an array of Integers.
+     */
+    public void add(int value) throws IllegalStateException {
+        this.checkCurrentArray();
+        this.currentArray.addValue(new ExtraInt(this.currentArray.size(), value));
+    }
+
+    /**
+     * Add a value to the current object.
+     * @param field The name of the field that holds the value.
+     * @param value The value to add.
+     * @throws IllegalStateException When not currently building an object.
+     */
+    public void add(String field, int value) throws IllegalStateException {
+        this.checkCurrentObject();
+        this.currentObject.setValue(new ExtraInt(field, value));
+    }
+
     /**
      * Stop building extra data and get the final object.
      * Once close is called, no other operation can be done.
diff --git a/src/main/java/org/pasteque/coreutil/extra/package-info.java b/src/main/java/org/pasteque/coreutil/extra/package-info.java
index 9312c4b..fd266bb 100644
--- a/src/main/java/org/pasteque/coreutil/extra/package-info.java
+++ b/src/main/java/org/pasteque/coreutil/extra/package-info.java
@@ -8,5 +8,9 @@
  * values. All values of {@link org.pasteque.coreutil.extra.ExtraData}
  * implementations are non-null. When the value is null, use an explicit
  * {@link org.pasteque.coreutil.extra.ExtraNull}.</p>
+ * <p>Extra objects will be found only in the major classes and their
+ * associated DTO from coreutil. Other packages will have the semantic values
+ * instead and convert them to extra data only when creating a major version
+ * of itself through transition interfaces.</p>
  */
 package org.pasteque.coreutil.extra;
diff --git a/src/main/java/org/pasteque/major/domain/MajorCashRegister.java b/src/main/java/org/pasteque/major/domain/MajorCashRegister.java
index 0920e82..85f3616 100644
--- a/src/main/java/org/pasteque/major/domain/MajorCashRegister.java
+++ b/src/main/java/org/pasteque/major/domain/MajorCashRegister.java
@@ -1,6 +1,7 @@
 package org.pasteque.major.domain;
 
 import org.pasteque.coreutil.datatransfer.dto.CashRegisterDTO;
+import org.pasteque.coreutil.extra.ExtraObject;
 
 /**
  * <p>Model for a cash register. Tickets are associated to a cash register
@@ -14,6 +15,8 @@ public class MajorCashRegister
     private String label;
     /** {@see getNextTicketNumber()} */
     private int nextTicketNumber;
+    /** See {@link getExtra()}. */
+    private ExtraObject extra;
 
     /**
      * Create from all fields.
@@ -21,24 +24,28 @@ public class MajorCashRegister
      * @param label See {@link getLabel()}.
      * @param nextTicketNumber The number to assign to the next ticket
      * from this cash register.
+     * @param extra See {@link getExtra()}.
      */
     public MajorCashRegister(
             String reference,
             String label,
-            int nextTicketNumber) {
+            int nextTicketNumber,
+            ExtraObject extra) {
         this.reference = reference;
         this.label = label;
         this.nextTicketNumber = nextTicketNumber;
+        this.extra = extra;
     }
 
     /**
-     * Create from a DTO. All data are copied to break references.
+     * Create from a DTO.
      * @param dto The DTO to convert.
      */
     public MajorCashRegister(CashRegisterDTO dto) {
-        this.reference = new String(dto.getReference());
-        this.label = new String(dto.getLabel());
+        this.reference = dto.getReference();
+        this.label = dto.getLabel();
         this.nextTicketNumber = dto.getNextTicketNumber();
+        this.extra = dto.getExtra();
     }
 
     /**
@@ -77,4 +84,12 @@ public class MajorCashRegister
     /* package */ final void revertNextTicketNumber() {
         this.nextTicketNumber--;
     }
+
+    /**
+     * Get all other data.
+     * @return The root object of extra data.
+     */
+    public final ExtraObject getExtra() {
+        return this.extra;
+    }
 }
diff --git a/src/main/java/org/pasteque/major/domain/MajorOrder.java b/src/main/java/org/pasteque/major/domain/MajorOrder.java
index 7f5030d..6fca466 100644
--- a/src/main/java/org/pasteque/major/domain/MajorOrder.java
+++ b/src/main/java/org/pasteque/major/domain/MajorOrder.java
@@ -22,6 +22,7 @@ public final class MajorOrder implements OrderTransition
     private final Price2 finalTaxedPrice;
     private final ImmutableList<MajorLine> lines;
     private final Discount discount;
+    /** See {@link getExtra()}. */
     private final ExtraObject extra;
 
     /**
diff --git a/src/main/java/org/pasteque/major/domain/MajorZTicket.java b/src/main/java/org/pasteque/major/domain/MajorZTicket.java
index 898b014..7404998 100644
--- a/src/main/java/org/pasteque/major/domain/MajorZTicket.java
+++ b/src/main/java/org/pasteque/major/domain/MajorZTicket.java
@@ -2,6 +2,7 @@ package org.pasteque.major.domain;
 
 import java.util.Date;
 import java.util.List;
+import org.pasteque.coreutil.extra.ExtraObject;
 import org.pasteque.coreutil.constants.FiscalTicketType;
 import org.pasteque.coreutil.datatransfer.dto.FiscalTicketDTO;
 
@@ -23,7 +24,8 @@ public final class MajorZTicket
             MajorCashSession session,
             Date closeDate,
             int closeType,
-            List<Movement> endAmounts) {
+            List<Movement> endAmounts,
+            ExtraObject extra) {
         // TODO: not implemented
         throw new UnsupportedOperationException("Not implemented yet");
     }