diff --git a/README.md b/README.md
index 4e44853..77122f0 100644
--- a/README.md
+++ b/README.md
@@ -4,9 +4,18 @@ Embed "things" in your markdown files.
 
 Given the same input, `emdbed` should give idempotent results.
 
+To create an `emdbed` section, use a header and footer as follows
+```text
+<!-- emdbed: <file> [~<language>] [L<start-line>|/<start-regex>/] [L<end-line>|/<end-regex>/]
+<!-- /emdbed -->
+```
+
+The regex is [Go flavored](https://golang.org/s/re2syntax), which you can test on [regex101](https://regex101.com/).
+
 ## Examples
 
-The following are generated using [readme.go](readme.go) and `go generate ./...`.
+The following are generated using [readme.go](readme.go) and `go generate ./...`.  
+Check the raw markdown for the header selectors used.
 
 An entire file: