--- /dev/null
+<?php
+
+namespace Drupal\layout_builder;
+
+/**
+ * Defines an interface for an object that stores layout sections for defaults.
+ *
+ * @internal
+ * Layout Builder is currently experimental and should only be leveraged by
+ * experimental modules and development releases of contributed modules.
+ * See https://www.drupal.org/core/experimental for more information.
+ */
+interface DefaultsSectionStorageInterface extends SectionStorageInterface {
+
+ /**
+ * Determines if the defaults allow custom overrides.
+ *
+ * @return bool
+ * TRUE if custom overrides are allowed, FALSE otherwise.
+ */
+ public function isOverridable();
+
+ /**
+ * Sets the defaults to allow or disallow overrides.
+ *
+ * @param bool $overridable
+ * TRUE if the display should allow overrides, FALSE otherwise.
+ *
+ * @return $this
+ */
+ public function setOverridable($overridable = TRUE);
+
+}