diff --git a/handbook/survey/ententryfields.html b/handbook/survey/ententryfields.html
index f47560c1e..64f252824 100644
--- a/handbook/survey/ententryfields.html
+++ b/handbook/survey/ententryfields.html
@@ -25,6 +25,12 @@
   <li><b>marking</b> e.g. Tag or Paint
   </ul>
 <p>See below for explanations.
+  
+  <h3>Names of identifiers and files</h3>
+<p>Always use <b>lower case</b> in names of caves, despite what you might see in historical data. 
+<p>So a new cave would be 2023-zz-01 and its entrances would be 2023-zz-01a, 2023-zz-01b and 2023-zz-01c. 
+<p>This is to prevent confusion between Windows and Linux machines, and unintentional deletion of data.
+  
 <h2>List of New Entrance/Entrance_data fields</h2>
   <dl>
     <dt>non_public</dt>