diff --git a/schedule.md b/schedule.md
index 764da30..fdf4f5d 100644
--- a/schedule.md
+++ b/schedule.md
@@ -7,6 +7,8 @@ nav_order: 2
 
 # Weekly Office Hours
 
+We use an [online sign-up system](https://oh.data8.org/) to help keep track of everyone.
+
 {% for schedule in site.schedules %}
 {{ schedule }}
 {% endfor %}