add note about third and fourth screws

diff --git a/curriculum/challenge-bot.scm b/curriculum/challenge-bot.scm
index f0a9893855f0de51334ea8b91a044ed4a2841fc1..7d83019642cc6cbc3504fc23fb332546268a3d36 100644 (file)
--- a/curriculum/challenge-bot.scm
+++ b/curriculum/challenge-bot.scm
@@ -272,7 +272,11 @@
             furthest away from the first hole.
             then insert and tighten the screw as before.])))
    (subsection
-    :title [third and fourth hole and screw]))
+    :title [third and fourth hole and screw]
+    (p [even though the arduino is pretty well attached with just 2
+             screws, we will add a third and fourth.
+             this gives practice drilling and tightening screws.
+             it also keeps the arduino fixed even more rigidly.])))
   (section
    :title [breadboard])
   (section