diff --git a/README.md b/README.md
index 70492d0..b356627 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_1065 TILs and counting..._
+_1066 TILs and counting..._
 
 ---
 
@@ -48,6 +48,7 @@ _1065 TILs and counting..._
 * [React Testing Library](#react-testing-library)
 * [ReasonML](#reasonml)
 * [Ruby](#ruby)
+* [sed](#sed)
 * [Shell](#shell)
 * [Tailwind CSS](#tailwind-css)
 * [tmux](#tmux)
@@ -923,6 +924,10 @@ _1065 TILs and counting..._
 - [Wrap Things In An Array, Even Hashes](ruby/wrap-things-in-an-array-even-hashes.md)
 - [Zero Padding](ruby/zero-padding.md)
 
+### sed
+
+- [Use An Alternative Delimiter In A Substitution](sed/use-an-alternative-delimiter-in-a-substitution.md)
+
 ### Shell
 
 - [Check If The First Argument Is Given](shell/check-if-the-first-argument-is-given.md)
diff --git a/sed/use-an-alternative-delimiter-in-a-substitution.md b/sed/use-an-alternative-delimiter-in-a-substitution.md
new file mode 100644
index 0000000..fc79a89
--- /dev/null
+++ b/sed/use-an-alternative-delimiter-in-a-substitution.md
@@ -0,0 +1,33 @@
+# Use An Alternative Delimiter In A Substitution
+
+A pretty standard sed substitution command is going to use `/` (the forward
+slash) as the delimiter. The delimiter separates the different parts of the
+command.
+
+```bash
+$ sed 's/critter/creature/' animals.txt
+```
+
+The first delimiter marks the beginning of the regular express to be replaced.
+That expression is everything up to the next delimiter. Then the substute
+expression starts up until the next delimiter.
+
+There is nothing special about the `/` as the delimiter, it just happens to be
+the most commonly used character.
+
+In fact, any visible character can be used as the delimiter with sed.
+
+Some other common ones are `:`, `|`, and `_`. I like how the `pipe` character
+looks.
+
+```bash
+$ sed 's|critter|creature|' animals.txt
+```
+
+But like I said, any visible character will work. If you wanted, you could use
+`Q` though that'll look strange and could cause some confusion when reading
+through your script.
+
+```bash
+$ sed 'sQcritterQcreatureQ' animals.txt
+```