diff --git a/map-basics.md b/map-basics.md
index 4be163f..45ec05d 100644
--- a/map-basics.md
+++ b/map-basics.md
@@ -34,7 +34,8 @@ Assuming you copied the template.xml file to your mod's **maps** directory: Copy
 After entering the map, open the editor (_Tab_) and press _F11_. If your map template is correctly set up this will load the map template, and populate the map with wall data (i.e. black pixels will become solid  black blocks). Next, press F12. This will distribute wall tiles taken from the [[tileset|tilesets]] along the walls. This process can take a few seconds for very large maps.
 
 What happens in detail:
-* Delete all tiles on [[Layer 5|layers]]
+* Delete all tiles with tileset ID **1-4** on [[Layer 5|layers]]
+  * Tiles outside of this range are not affected; while you can place other tiles safely on this layer it's better to not use it unless you absolutely have to.
 * Find edges between wall and free space and determine [surface normals](https://en.wikipedia.org/wiki/Normal_(geometry))
 * Place tiles on [[Layer 5|layers]] so that all edges on the map are covered and the tiles are properly rotated.