Merge branch 'twbs/v4-dev' into dropdown-keyboard

# Conflicts:
#	js/src/dropdown.js

2 files changed, 34 insertions, 18 deletions

diff --git a/docs/utilities/position.md b/docs/utilities/position.md
new file mode 100644
index 000000000..6b8268c48
--- /dev/null
+++ b/docs/utilities/position.md
@@ -0,0 +1,31 @@
+---
+layout: docs
+title: Position
+group: utilities
+---
+
+Position utilities are helpful for quickly placing a component outside the normal document flow. Choose from a handful of fixed or sticky position classes as needed.
+
+### Fixed top
+
+Position an element at the top of the viewport, from edge to edge. Be sure you understand the ramifications of fixed position in your project; you may need to add aditional CSS.
+
+{% highlight html %}
+<div class="fixed-top">...</div>
+{% endhighlight %}
+
+### Fixed bottom
+
+Position an element at the bottom of the viewport, from edge to edge. Be sure you understand the ramifications of fixed position in your project; you may need to add aditional CSS.
+
+{% highlight html %}
+<div class="fixed-bottom">...</div>
+{% endhighlight %}
+
+### Sticky top
+
+Position an element at the top of the viewport, from edge to edge, but only after you scroll past it. The `.sticky-top` utility uses CSS's `position: sticky`, which isn't fully supported in all browsers.
+
+{% highlight html %}
+<div class="sticky-top">...</div>
+{% endhighlight %}
diff --git a/docs/utilities/sizing-and-positioning.md b/docs/utilities/sizing.md
index a6de778ca..eabb4653a 100644
--- a/docs/utilities/sizing-and-positioning.md
+++ b/docs/utilities/sizing.md
@@ -1,27 +1,12 @@
 ---
 layout: docs
-title: Sizing and positioning
+title: Sizing
 group: utilities
 ---
 
-## Fixed positioning
+Easily make an element as wide or as tall (relative to its parent) with our width and height utilities. Includes support for `25%`, `50%`, `75%`, and `100%` by default.
 
-The `.pos-f-t` class can be used to easily position elements at the top of the viewport and make them as wide as the viewport. **Be sure you understand the ramifications of fixed-position elements within your project.** Here's how the class is defined:
-
-{% highlight scss %}
-.pos-f-t {
-  position: fixed;
-  top: 0;
-  right: 0;
-  left: 0;
-  z-index: $zindex-navbar-fixed;
-}
-{% endhighlight %}
-
-
-## Width and height
-
-Easily make an element as wide or as tall (relative to its parent) with our width and height utilities. Includes support for `25%`, `50%`, `75%`, and `100%`.
+Width and height utilities are generated from the `$sizes` Sass map in `_variables.scss`. Modify those values as you need to generate different utilities here.
 
 {% example html %}
 <div class="w-25 p-3" style="background-color: #eee;">Width 25%</div>