From edf376ce0d33d6157e9a1be94dfe6c8af15ae7df Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Tue, 12 Apr 2016 17:15:10 -0700
Subject: [PATCH 1/2] Fix: gcode_T using non-existent Z offset

As noted by @snowzach in #3461
---
 Marlin/Marlin_main.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index d0cdf0a49..8fe7bc211 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -6178,10 +6178,10 @@ inline void gcode_T(uint8_t tmp_extruder) {
             // Offset extruder, make sure to apply the bed level rotation matrix
             vector_3 tmp_offset_vec = vector_3(extruder_offset[X_AXIS][tmp_extruder],
                                                extruder_offset[Y_AXIS][tmp_extruder],
-                                               extruder_offset[Z_AXIS][tmp_extruder]),
+                                               0),
                      act_offset_vec = vector_3(extruder_offset[X_AXIS][active_extruder],
                                                extruder_offset[Y_AXIS][active_extruder],
-                                               extruder_offset[Z_AXIS][active_extruder]),
+                                               0),
                      offset_vec = tmp_offset_vec - act_offset_vec;
             offset_vec.apply_rotation(plan_bed_level_matrix.transpose(plan_bed_level_matrix));
             current_position[X_AXIS] += offset_vec.x;

From 46881c846c2a13a0e9c2882d171182299921bd90 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Tue, 12 Apr 2016 17:16:58 -0700
Subject: [PATCH 2/2] Add comments for extruder offset options

---
 Marlin/Marlin_main.cpp | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 8fe7bc211..486e0e734 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -322,16 +322,16 @@ static uint8_t target_extruder;
 // Extruder offsets
 #if EXTRUDERS > 1
   #ifndef EXTRUDER_OFFSET_X
-    #define EXTRUDER_OFFSET_X { 0 }
+    #define EXTRUDER_OFFSET_X { 0 } // X offsets for each extruder
   #endif
   #ifndef EXTRUDER_OFFSET_Y
-    #define EXTRUDER_OFFSET_Y { 0 }
+    #define EXTRUDER_OFFSET_Y { 0 } // Y offsets for each extruder
   #endif
   float extruder_offset[][EXTRUDERS] = {
     EXTRUDER_OFFSET_X,
     EXTRUDER_OFFSET_Y
     #if ENABLED(DUAL_X_CARRIAGE)
-      , { 0 } // supports offsets in XYZ plane
+      , { 0 } // Z offsets for each extruder
     #endif
   };
 #endif
@@ -5144,7 +5144,12 @@ inline void gcode_M206() {
 #if EXTRUDERS > 1
 
   /**
-   * M218 - set hotend offset (in mm), T<extruder_number> X<offset_on_X> Y<offset_on_Y>
+   * M218 - set hotend offset (in mm)
+   *
+   *   T<tool>
+   *   X<xoffset>
+   *   Y<yoffset>
+   *   Z<zoffset> - Available with DUAL_X_CARRIAGE
    */
   inline void gcode_M218() {
     if (setTargetedHotend(218)) return;