Sticky boards are used to help monitor Varroa mite levels and to check the efficacy of the Varroa treatments you are using.
Place the sticky board on the floor of the hive with the cut out "V" towards the entrance. Then apply your Varroa treatment. In 24 hours, remove the sticky board and count how many Varroa are found. This will give you an indication of the level of infestation, and how well the Varroa treatment is working.