Update grid.json

grid.json

@@ -306,6 +306,17 @@
                 11
             ],
             "color": "#898989"
+        },
+        {
+            "start": [
+                6,
+                15
+            ],
+            "end": [
+                6,
+                15
+            ],
+            "color": "#898989"
         }
     ]
 }