diff --git a/SKILL.md b/SKILL.md
index 8a9273e..665043b 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -70,6 +70,11 @@ printf '*\n' > ~/Git/<repo>/.reference/.gitignore
 - The `.gitignore` **inside** `.reference/` contains a single `*`. Ignore the
   whole folder there, not in the repo's root `.gitignore`: the folder is then
   self-contained and stays untracked even if the root ignore file is rewritten.
+- **Any repo cloned to study, port, or compare against is reference material.**
+  When asked to "check out this repo" (e.g. to reimplement it in another
+  language), create `.reference/` and its `.gitignore` as the very first step
+  and clone straight into it — never into the working root, even when the
+  project is not a git repo yet.
 - Clone reference repos inside it:
   `git clone --depth 1 <url> .reference/<name>`. Do not vendor them into
   `Sources/` or `vendor/`.