diff --git a/doc/user-manual/fpakc_UserManual.tex b/doc/user-manual/fpakc_UserManual.tex
index 27c0a32..469165c 100644
--- a/doc/user-manual/fpakc_UserManual.tex
+++ b/doc/user-manual/fpakc_UserManual.tex
@@ -620,6 +620,9 @@ make
         \begin{itemize}
           \item \textbf{index}. Integer.
             Index of the edge surface as defined in the mesh file.
+          \item \textbf{particles}. Array of characters.
+            Size equal to the number of species.
+            Each element of the array is the name of the \textbf{boundaries.particles} that the species will experience when interacting with the edge in this physical surface.
         \end{itemize}
 
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