diff --git a/docs/Scheme-code-conventions.md b/docs/Scheme-code-conventions.md
index 1ce0182c..0a425187 100644
--- a/docs/Scheme-code-conventions.md
+++ b/docs/Scheme-code-conventions.md
@@ -373,6 +373,25 @@ Use `:` to explicitly note the namespace from which a name comes. **Only** use w
 
     foo:procedure
 
+### Low-level and/or internal procedures (% or _)
+
+Use `%` or `_` to prefix low-level and/or internal procedures.
+
+    %make-raw-structure
+    %adjust-settings
+    _py-eval
+    _curl-get-opts
+
+Although not necessary, it is not rare to see low-level/internal procedures and high-level/exposed procedures sharing their name, except for the prefix symbol. Sometimes the high-level/exposed procedures work as wrappers around the low-level/internal ones.
+
+```Scheme
+%retrieve-data ;; low-level/internal
+retrieve-data  ;; high-level/exposed - a wrapper around %retrieve-data
+
+_py-eval ;; deals with C pointers and Python stuff
+py-eval  ;; deals only with Scheme data types
+```
+
 # Comments 
 
 Write comments only where the code is incapable of explaining itself. This is not a recommendation to avoid comments, but rather an incentive to **prefer self-explanatory code over explanatory comments**.