diff --git a/src/main/kotlin/me/tech/mcchestui/GUI.kt b/src/main/kotlin/me/tech/mcchestui/GUI.kt
index cd7fbda..743bea6 100644
--- a/src/main/kotlin/me/tech/mcchestui/GUI.kt
+++ b/src/main/kotlin/me/tech/mcchestui/GUI.kt
@@ -7,20 +7,18 @@
 
 package me.tech.mcchestui
 
-import me.tech.mcchestui.item.GUIItem
+import me.tech.mcchestui.attached.*
+import me.tech.mcchestui.item.*
 import me.tech.mcchestui.listeners.*
-import me.tech.mcchestui.listeners.item.*
 import me.tech.mcchestui.listeners.hotbar.*
-import me.tech.mcchestui.utils.GUICloseEvent
-import me.tech.mcchestui.utils.GUIDragItemEvent
-import me.tech.mcchestui.utils.GUIItemPickupEvent
-import me.tech.mcchestui.utils.GUIItemPlaceEvent
-import me.tech.mcchestui.utils.GUISlotClickEvent
+import me.tech.mcchestui.listeners.item.*
+import me.tech.mcchestui.utils.*
 import net.kyori.adventure.text.Component
 import org.bukkit.entity.Player
 import org.bukkit.event.*
 import org.bukkit.inventory.Inventory
 import org.bukkit.inventory.ItemStack
+import org.bukkit.inventory.PlayerInventory
 import org.bukkit.plugin.java.JavaPlugin
 
 /**
@@ -31,24 +29,10 @@ import org.bukkit.plugin.java.JavaPlugin
  * @param y must be above 0 and less than rows.
  * @param type [GUIType] for the coordinates to map to.
  * @return [Int] representing the slot index.
- * @throws IllegalArgumentException if x or y coordinates are invalid.
  */
 fun toSlot(x: Int, y: Int, type: GUIType): Int {
-	if(x < 1 || y < 1) {
-		throw IllegalArgumentException("x or y cannot be below 1.")
-	}
-
-	if(x > type.slotsPerRow) {
-		throw IllegalArgumentException("x must be between 1 and ${type.slotsPerRow}.")
-	}
-
-	if(y > type.rows) {
-		throw IllegalArgumentException("y must be between 1 and ${type.slotsPerRow}.")
-	}
-
 	return (x - 1) + ((y - 1) * type.slotsPerRow)
 }
-fun fromSlot(s: Int, type: GUIType) = Pair(s % type.slotsPerRow, s / type.slotsPerRow)
 
 /**
  * Construct a [GUI.Slot] to be placed in a [GUI].
@@ -62,11 +46,22 @@ fun GUI.guiSlot(builder: GUI.Slot.() -> Unit): GUI.Slot {
 }
 
 class GUI(
-	plugin: JavaPlugin,
+	internal val plugin: JavaPlugin,
 	val title: Component,
 	val type: GUIType,
-	private val render: GUI.() -> Unit
+	/**
+	 * Bukkit [Inventory] of the [GUI].
+	 *
+	 * Do not open [GUI] from this reference as it may
+	 * lead to undefined behavior.
+	 */
+	val bukkitInventory: Inventory,
+	attached: Boolean,
+	private val render: GUI.() -> Unit = { }
 ) {
+	constructor(plugin: JavaPlugin, inventory: PlayerInventory)
+		: this(plugin, Component.empty(), GUIType.Chest(rows = 4), inventory, true)
+
 	/**
 	 * Allow for [ItemStack] to be placed in the [GUI].
 	 */
@@ -127,12 +122,10 @@ class GUI(
 	 * Do not open [GUI] from this reference as it may
 	 * lead to undefined behavior.
 	 */
-	val bukkitInventory: Inventory = if(type is GUIType.Chest) {
-		plugin.server.createInventory(null, type.slotsPerRow * type.rows, title)
-	} else {
-		plugin.server.createInventory(null, type.inventoryType, title)
-	}
 
+	/**
+	 * Slots used by the [GUI].
+	 */
 	internal var slots = arrayOfNulls<Slot>(type.slotsPerRow * type.rows)
 
 	/**
@@ -140,17 +133,39 @@ class GUI(
 	 */
 	internal var templateSlots = mutableMapOf<Char, Slot>()
 
-	private val eventListeners = listOf(
-		GUISlotClickListener(this),
-
-		GUIItemPickupListener(this),
-		GUIItemPlaceListener(this),
-		GUIItemDragListener(this),
+	/**
+	 * [PlayerInventory] attached to the [GUI] that acts
+	 * like a [GUI].
+	 */
+	internal var attachedGui: GUI? = null
 
-		GUIHotbarListener(this),
+	/**
+	 * @return Whether another [GUI] has been attached to this one.
+	 */
+	val hasAttachedGui: Boolean
+		get() = attachedGui != null
 
-		GUICloseListener(this)
-	)
+	/**
+	 * [PlayerInventory] cache for when an [attachedGui] is present.
+	 * Will by default use the [MemoryAttachedInventoryCache] which will lose data
+	 * if the server closes while a player is actively using the [attachedGui].
+	 */
+	internal var attachedInventoryCache: AttachedInventoryCache = MemoryAttachedInventoryCache
+
+	private val eventListeners = if(!attached) {
+		listOf(
+			GUISlotClickListener(this),
+			GUICloseListener(this),
+			GUIItemPlaceListener(this),
+			GUIItemPickupListener(this),
+			GUIItemDragListener(this),
+			GUIHotbarListener(this)
+		)
+	} else {
+		listOf(
+			GUISlotClickListener(this)
+		)
+	}
 
 	/**
 	 * Define weather the [GUI] has been unregistered.
@@ -159,10 +174,7 @@ class GUI(
 	internal var unregistered = false
 
 	init {
-		eventListeners.forEach {
-			plugin.server.pluginManager
-				.registerEvents(it, plugin)
-		}
+	    registerListeners(plugin)
 	}
 
 	/**
@@ -193,7 +205,21 @@ class GUI(
 	 * @param slot slot
 	 */
 	fun slot(i: Int, slot: Slot) {
-		if(i > bukkitInventory.size) {
+		if(i >= bukkitInventory.size) {
+			// run slot in attached ui instead.
+			if(hasAttachedGui) {
+				var attachedUiIndex = i - (type.slotsPerRow * type.rows)
+				attachedUiIndex = when {
+					(attachedUiIndex + 9) >= 36 -> attachedUiIndex - 27
+					else -> attachedUiIndex + 9
+				}
+
+				attachedGui?.slot(
+					attachedUiIndex,
+					slot
+				)
+			}
+
 			return
 		}
 
@@ -318,6 +344,16 @@ class GUI(
 		return bukkitInventory == other
 	}
 
+	/**
+	 * Register all [Listener] associated with the [GUI].
+	 */
+	private fun registerListeners(plugin: JavaPlugin) {
+		eventListeners.forEach {
+			plugin.server.pluginManager
+				.registerEvents(it, plugin)
+		}
+	}
+
 	/**
 	 * Mark a [GUI] as unregistered and remove its [Listener].
 	 */
diff --git a/src/main/kotlin/me/tech/mcchestui/GUIType.kt b/src/main/kotlin/me/tech/mcchestui/GUIType.kt
index 4bac8c1..81425f5 100644
--- a/src/main/kotlin/me/tech/mcchestui/GUIType.kt
+++ b/src/main/kotlin/me/tech/mcchestui/GUIType.kt
@@ -1,19 +1,32 @@
 package me.tech.mcchestui
 
+import net.kyori.adventure.text.Component
+import org.bukkit.Bukkit
 import org.bukkit.event.inventory.InventoryType
+import org.bukkit.inventory.Inventory
+
+sealed class GUIType(
+	val slotsPerRow: Int,
+	val rows: Int,
+	val inventoryType: InventoryType
+) {
+	/**
+	 * @return total amount of slots a [InventoryType] can hold.
+	 */
+	val totalSlots: Int
+		get() = slotsPerRow * rows
+
+	 internal open fun createBukkitInventory(
+		 title: Component
+	 ): Inventory {
+		 return Bukkit.createInventory(null, inventoryType, title)
+	 }
 
-sealed interface GUIType {
-	 val slotsPerRow: Int
-	 val rows: Int
-	 val inventoryType: InventoryType
-
-	 data class Chest(override val rows: Int) : GUIType {
-		 override val slotsPerRow: Int
-			 get() = 9
-
-		 override val inventoryType: InventoryType
-			 get() = InventoryType.CHEST
-
+	 class Chest(rows: Int) : GUIType(
+		 slotsPerRow = 9,
+		 rows,
+		 inventoryType = InventoryType.CHEST
+	 ) {
 		 init {
 			 if(rows < 1 || rows > 6) {
 				 throw IllegalArgumentException(
@@ -21,27 +34,21 @@ sealed interface GUIType {
 				 )
 			 }
 		 }
-	 }
-
-	 data object Dispenser : GUIType {
-		override val slotsPerRow: Int
-			get() = 3
 
-		override val rows: Int
-			get() = 3
-
-		override val inventoryType: InventoryType
-			get() = InventoryType.DISPENSER
-	}
-
-	data object Hopper : GUIType {
-		override val slotsPerRow: Int
-			get() = 5
-
-		override val rows: Int
-			get() = 1
+		 override fun createBukkitInventory(title: Component): Inventory {
+			 return Bukkit.createInventory(null, slotsPerRow * rows, title)
+		 }
+	 }
 
-		override val inventoryType: InventoryType
-			get() = InventoryType.HOPPER
-	}
+	 data object Dispenser : GUIType(
+		 slotsPerRow = 3,
+		 rows = 3,
+		 inventoryType = InventoryType.HOPPER
+	 )
+
+	data object Hopper : GUIType(
+		slotsPerRow = 5,
+		rows = 1,
+		inventoryType = InventoryType.HOPPER
+	)
 }
\ No newline at end of file
diff --git a/src/main/kotlin/me/tech/mcchestui/attached/AttachedGUI.kt b/src/main/kotlin/me/tech/mcchestui/attached/AttachedGUI.kt
new file mode 100644
index 0000000..9fc859e
--- /dev/null
+++ b/src/main/kotlin/me/tech/mcchestui/attached/AttachedGUI.kt
@@ -0,0 +1,29 @@
+package me.tech.mcchestui.attached
+
+import me.tech.mcchestui.GUI
+import org.bukkit.entity.Player
+import org.bukkit.inventory.PlayerInventory
+
+/**
+ * Attach a [PlayerInventory] to a [GUI] to be used as a
+ * secondary menu alongside the parent [GUI].
+ *
+ * @param player [PlayerInventory] to be used.
+ */
+fun GUI.attach(player: Player) {
+    // cache inventory.
+    attachedInventoryCache.saveInventory(player)
+    player.inventory.storageContents = emptyArray()
+
+    attach(player.inventory)
+}
+
+/**
+ * Attach a [PlayerInventory] to a [GUI] to be used as a
+ * secondary menu alongside the parent [GUI].
+ *
+ * @param playerInventory inventory to be used.
+ */
+private fun GUI.attach(playerInventory: PlayerInventory) {
+    attachedGui = GUI(plugin, playerInventory)
+}
\ No newline at end of file
diff --git a/src/main/kotlin/me/tech/mcchestui/attached/AttachedInventoryCache.kt b/src/main/kotlin/me/tech/mcchestui/attached/AttachedInventoryCache.kt
new file mode 100644
index 0000000..142dae5
--- /dev/null
+++ b/src/main/kotlin/me/tech/mcchestui/attached/AttachedInventoryCache.kt
@@ -0,0 +1,78 @@
+package me.tech.mcchestui.attached
+
+import me.tech.mcchestui.GUI
+import org.bukkit.entity.Player
+
+import org.bukkit.inventory.ItemStack
+import org.bukkit.inventory.PlayerInventory
+import java.util.*
+
+/**
+ * Used to cache the items removed from a [Player] when
+ * a [GUI.attachedGui] is being used.
+ *
+ * The items of the [Player] are restored when the GUICloseEvent is called
+ * on the parent [GUI].
+ * Contents of the [Player] inventory will then be restored.
+ */
+interface AttachedInventoryCache {
+    /**
+     * Save the storage contents of a [PlayerInventory] before the contents of
+     * the [GUI.attachedGui] override the [PlayerInventory].
+     *
+     * @param player
+     * @return whether the operation was a success.
+     */
+    fun saveInventory(player: Player): Boolean
+
+    /**
+     * Restore the storage contents of a [PlayerInventory] to their state
+     * before being overridden by the [GUI.attachedGui].
+     *
+     * @param player
+     * @return whether the operation was a success.
+     */
+    fun restoreInventory(player: Player): Boolean
+}
+
+/**
+ * Memory attached gui cache.
+ */
+internal object MemoryAttachedInventoryCache : AttachedInventoryCache {
+    private val cachedInventory = mutableMapOf<UUID, Array<ItemStack?>>()
+
+    override fun saveInventory(player: Player): Boolean {
+        cachedInventory[player.uniqueId] = player.inventory.storageContents
+
+        return true
+    }
+
+    override fun restoreInventory(player: Player): Boolean {
+        val inventory = cachedInventory[player.uniqueId]
+            ?: return false
+
+        player.inventory.storageContents = inventory
+        cachedInventory.remove(player.uniqueId)
+
+        return true
+    }
+}
+
+/**
+ * Attach a custom [AttachedInventoryCache] to a [GUI].
+ * By default, the [MemoryAttachedInventoryCache] is used.
+ */
+fun GUI.attachInventoryCache(cache: AttachedInventoryCache) {
+    attachedInventoryCache = cache
+}
+
+/**
+ * Restore a players inventory from the [AttachedInventoryCache].
+ *
+ * @param player player to cache.
+ * @param gui gui to cache for.
+ */
+internal fun restoreCachedInventory(player: Player, gui: GUI) {
+    player.inventory.storageContents = emptyArray()
+    gui.attachedInventoryCache.restoreInventory(player)
+}
\ No newline at end of file
diff --git a/src/main/kotlin/me/tech/mcchestui/listeners/GUICloseListener.kt b/src/main/kotlin/me/tech/mcchestui/listeners/GUICloseListener.kt
index deae2a3..5a2d590 100644
--- a/src/main/kotlin/me/tech/mcchestui/listeners/GUICloseListener.kt
+++ b/src/main/kotlin/me/tech/mcchestui/listeners/GUICloseListener.kt
@@ -1,6 +1,8 @@
 package me.tech.mcchestui.listeners
 
 import me.tech.mcchestui.GUI
+import me.tech.mcchestui.attached.restoreCachedInventory
+import org.bukkit.entity.Player
 import org.bukkit.event.EventHandler
 import org.bukkit.event.inventory.InventoryCloseEvent
 
@@ -11,6 +13,14 @@ internal class GUICloseListener(gui: GUI) : GUIEventListener(gui) {
             return
         }
 
+        if(gui.hasAttachedGui) {
+            player.inventory.storageContents = emptyArray()
+
+            gui.attachedGui?.unregister()
+
+            restoreCachedInventory(player as Player, gui)
+        }
+
         gui.onCloseInventory?.let { uiEvent ->
             uiEvent(this, player)
         }
diff --git a/src/main/kotlin/me/tech/mcchestui/listeners/hotbar/GUIHotbarListener.kt b/src/main/kotlin/me/tech/mcchestui/listeners/hotbar/GUIHotbarListener.kt
index 98e1dfb..82e5fad 100644
--- a/src/main/kotlin/me/tech/mcchestui/listeners/hotbar/GUIHotbarListener.kt
+++ b/src/main/kotlin/me/tech/mcchestui/listeners/hotbar/GUIHotbarListener.kt
@@ -2,6 +2,7 @@ package me.tech.mcchestui.listeners.hotbar
 
 import me.tech.mcchestui.GUI
 import me.tech.mcchestui.listeners.GUIEventListener
+import org.bukkit.Bukkit
 import org.bukkit.Material
 import org.bukkit.entity.Player
 import org.bukkit.event.EventHandler
@@ -11,10 +12,16 @@ import org.bukkit.event.inventory.InventoryClickEvent
 internal class GUIHotbarListener(gui: GUI) : GUIEventListener(gui) {
     @EventHandler(ignoreCancelled = true)
     internal fun InventoryClickEvent.hotBarSwitchToUIInventory() {
+        // we dont need hotbar swaps between two guis.
         if(!gui.isBukkitInventory(inventory)) {
             return
         }
 
+        if(gui.hasAttachedGui) {
+            isCancelled = true
+            return
+        }
+
         // player inv -> gui inv
         if(
             action !in HOTBAR_ACTIONS
@@ -54,10 +61,16 @@ internal class GUIHotbarListener(gui: GUI) : GUIEventListener(gui) {
 
     @EventHandler(ignoreCancelled = true)
     internal fun InventoryClickEvent.hotBarSwitchToPlayerInventory() {
+        // we dont need hotbar swaps between two guis.
         if(!gui.isBukkitInventory(inventory)) {
             return
         }
 
+        if(gui.hasAttachedGui) {
+            isCancelled = true
+            return
+        }
+
         // gui inv -> player inv
         if(
             action !in HOTBAR_ACTIONS
diff --git a/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemDragListener.kt b/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemDragListener.kt
index 4afbab1..8952af8 100644
--- a/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemDragListener.kt
+++ b/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemDragListener.kt
@@ -14,7 +14,7 @@ internal class GUIItemDragListener(gui: GUI) : GUIEventListener(gui) {
             return
         }
 
-        if(!gui.allowItemPlacement) {
+        if(!gui.allowItemPlacement || gui.hasAttachedGui) {
             isCancelled = true
             return
         }
diff --git a/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPickupListener.kt b/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPickupListener.kt
index 5b0c3a7..63aac2a 100644
--- a/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPickupListener.kt
+++ b/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPickupListener.kt
@@ -16,6 +16,11 @@ internal class GUIItemPickupListener(gui: GUI): GUIEventListener(gui) {
             return
         }
 
+        if(gui.hasAttachedGui) {
+            isCancelled = true
+            return
+        }
+
         // handle shift click
         if(
             action == InventoryAction.MOVE_TO_OTHER_INVENTORY
diff --git a/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPlaceListener.kt b/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPlaceListener.kt
index 915d98b..73834b2 100644
--- a/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPlaceListener.kt
+++ b/src/main/kotlin/me/tech/mcchestui/listeners/item/GUIItemPlaceListener.kt
@@ -16,6 +16,11 @@ internal class GUIItemPlaceListener(gui: GUI) : GUIEventListener(gui) {
             return
         }
 
+        if(gui.hasAttachedGui) {
+            isCancelled = true
+            return
+        }
+
         if(
             action == InventoryAction.MOVE_TO_OTHER_INVENTORY
             && isShiftClick
diff --git a/src/main/kotlin/me/tech/mcchestui/template/GUITemplate.kt b/src/main/kotlin/me/tech/mcchestui/template/GUITemplate.kt
index ba8475f..d841146 100644
--- a/src/main/kotlin/me/tech/mcchestui/template/GUITemplate.kt
+++ b/src/main/kotlin/me/tech/mcchestui/template/GUITemplate.kt
@@ -6,15 +6,8 @@ import me.tech.mcchestui.guiSlot
 /**
  * Representing the structure of the GUI Template.
  */
-data class GUITemplate(
-    var firstRow: String? = null,
-    var secondRow: String? = null,
-    var thirdRow: String? = null,
-    var fourthRow: String? = null,
-    var fifthRow: String? = null,
-    var sixthRow: String? = null,
-
-    var rows: String? = null
+class GUITemplate(
+    private val rows: Array<out String>
 ) {
     /**
      * Converts [GUITemplate] into a [Map].
@@ -26,21 +19,23 @@ data class GUITemplate(
      * @return list of characters mapped to the row.
      */
     internal fun toMap(): Map<Int, List<Char>> {
-        return rowsMap()
-            .toMutableMap()
-            .apply { putAll(selectRowsMap().filterValues { it.isNotEmpty() }) }
-    }
+        if(rows.isEmpty()) {
+            return emptyMap()
+        }
 
-    private fun rowsMap(): Map<Int, List<Char>> {
-        return rows
-            ?.split("\n")
-            ?.withIndex()
-            ?.associate { it.index + 1 to toCharList(it.value) }
-            ?: emptyMap()
-    }
+        if(rows.size == 1) {
+            val row = rows.first()
+            if(row.contains("\n")) {
+                return row
+                    .split("\n")
+                    .withIndex()
+                    .associate { it.index + 1 to toCharList(it.value) }
+            }
+
+            return mapOf(1 to toCharList(row))
+        }
 
-    private fun selectRowsMap(): Map<Int, List<Char>> {
-        return listOf(firstRow, secondRow, thirdRow, fourthRow, fifthRow, sixthRow)
+        return rows
             .withIndex()
             .associate { it.index + 1 to toCharList(it.value) }
     }
@@ -81,10 +76,10 @@ fun GUI.addTemplateSlot(char: Char, slot: GUI.Slot) {
 /**
  * Structure the template of the [GUI].
  *
- * @param builder template builder
+ * @param template [GUI] string template.
  */
-fun GUI.template(builder: GUITemplate.() -> Unit) {
-    val map = GUITemplate().apply(builder)
+fun GUI.template(vararg template: String) {
+    val map = GUITemplate(template)
         .toMap()
 
     for((yIndex, chars) in map) {
diff --git a/src/main/kotlin/me/tech/mcchestui/utils/GUIHelper.kt b/src/main/kotlin/me/tech/mcchestui/utils/GUIHelper.kt
index dc8aedf..bed62da 100644
--- a/src/main/kotlin/me/tech/mcchestui/utils/GUIHelper.kt
+++ b/src/main/kotlin/me/tech/mcchestui/utils/GUIHelper.kt
@@ -25,7 +25,7 @@ fun gui(
 	type: GUIType,
 	render: GUI.() -> Unit
 ): GUI {
-	return GUI(plugin, title, type, render).apply(render)
+	return GUI(plugin, title, type, type.createBukkitInventory(title), false, render).apply(render)
 }
 
 /**
@@ -41,6 +41,11 @@ fun HumanEntity.openGUI(gui: GUI) {
 	openInventory(gui.bukkitInventory)
 }
 
+/**
+ * Anonymous function to construct new [GUI].
+ */
+typealias GUIBuilder = GUI.() -> Unit
+
 /**
  * Event when an [ItemStack] interaction is preformed with a [GUI].
  */