Add .grid-container` to docs

diff --git a/docs/pages/xy-grid.md b/docs/pages/xy-grid.md
index 3724f7443ac8d69ac832ae28814b55bedc266641..c40d99c97ce62279d7d2bcf705d621d076cba28a 100644 (file)
--- a/docs/pages/xy-grid.md
+++ b/docs/pages/xy-grid.md
@@ -79,7 +79,21 @@ To define a grid type, simple set `.margin-gutters` or `.padding-gutters` on the
   <div class="medium-6 large-8 cell">12/6/8 cells</div>
 </div>
 ```
+---
+
+## Grid Container
+
+The grid defaults to the full width of its container. In order to contain the grid, use the `.grid-container` class.
 
+```html
+<div class="grid-container">
+  <div class="grid">
+    <div class="cell small-4">cell</div>
+    <div class="cell small-4">cell</div>
+    <div class="cell small-4">cell</div>
+  </div>
+</div>
+```
 ---
 
 ## Auto Sizing