diff --git a/.docs/grammars/axes.bnf b/.docs/grammars/axes.bnf
index 5150c21..6f5ae77 100644
--- a/.docs/grammars/axes.bnf
+++ b/.docs/grammars/axes.bnf
@@ -18,7 +18,7 @@ front 3 left 10 y 77 x 30 back 99
 <axis_name_absolute> ::= <axis_letters_absolute>
 	| "-" <axis_letters_absolute>
 
-<axis_name_relative> ::= front | back | left | right | up | down | "?"
+<axis_name_relative> ::= front | back | left | right | up | down | h | v | "?"
 
 <axis_letters_absolute> ::= x | y | z