diff --git a/resource/README.md b/resource/README.md
index 08857ad..65caa08 100644
--- a/resource/README.md
+++ b/resource/README.md
@@ -11,6 +11,7 @@ work.
 - `extract.py`: Takes the block type information from `blocks.json` and texture data
   from an unpacked Minecraft JAR, storing the result in `colors.json`
 - `generate.py`: Generates `block_types.rs` from `colors.json`
+- `sign_textures.py`: Generates all needed sign graphics from Minecraft assets
 
 In addition to these scripts, the JSON processor *jq* is a useful tool to work
 with MinedMap's resource metadata.
@@ -47,7 +48,8 @@ with MinedMap's resource metadata.
 
    If possible, the top texture of blocks should be used where different sides
    exist. Block types that should not be visible on the map are just set to
-   `null` in the JSON.
+   `null` in the JSON (or have a `null` `texture` field when other flags need
+   to be set, like for sign blocks).
 
    The `water`, `grass` and `foliage` flags control biome-dependent texture color modifiers.