diff --git a/bin/keyboardcomposer b/bin/keyboardcomposer
--- a/bin/keyboardcomposer
+++ b/bin/keyboardcomposer
@@ -360,6 +360,16 @@ class Sliders(BCF2000):
                 slider_var.set(0)
             else:
                 slider_var.set(1)
+        elif name.startswith("button-corner"):
+            button_num = int(name[13:]) - 1
+            if button_num == 1:
+                diff = 1
+            elif button_num == 3:
+                diff = -1
+            else:
+                return
+
+            kc.change_row(kc.current_row + diff)
 
 if __name__ == "__main__":
     parser = OptionParser()