diff --git a/docs/user/guide.md b/docs/user/guide.md
index b875ab04..fb61bb92 100644
--- a/docs/user/guide.md
+++ b/docs/user/guide.md
@@ -114,7 +114,8 @@ Choose one command:
   copies, but any copy can recover the seed.
 - **Custom:** thresholds 4 through 9 require `--shares` or `--indices`. For
   example, `ms32 create 4cash --shares 7` produces seven `cash` shares; any
-  four recover the seed.
+  four recover the seed. The identifier tells backups apart, so choose one
+  that no other backup you keep uses.
 
 More required shares make theft harder; fewer required shares make recovery
 easier.
diff --git a/src/codex32/_cli_parser.py b/src/codex32/_cli_parser.py
index c2472109..657a59b9 100644
--- a/src/codex32/_cli_parser.py
+++ b/src/codex32/_cli_parser.py
@@ -160,7 +160,7 @@ def parser(prog: str = "codex32", *, master_seed: bool = False) -> argparse.Argu
         "header",
         nargs="?",
         metavar="HEADER",
-        help="backup header or sharing threshold, such as 3cash or 3; omit for a single recovery card",
+        help="sharing threshold, such as 3, or threshold and identifier, such as 3cash, using an identifier no other backup you keep uses; omit for a single recovery card",
     )
     create.add_argument(
         "--bytes",