Our robbing screen has been born out of necessity this year as wasps and robbing bees have decimated many hives throughout NZ.
Stainless steel wire mesh on a timber frame fits snuggly on the front of your brood box with a small entrance way on the top of the frame. To really make the hive as impregnable as possible, add a hivegate as well: https://www.hiveworld.co.nz/product/hivegate/
This gives the home guard a fighting chance of blocking intruders. Robbers and wasps can smell the honey but cannot find their way in. The home bees, however, find their way out and can get back in the same way. If they are out when you put the robbing screen on, they will stay around the hive until they find their way in.
We would like to emphasise once again how important varroa control is to the strength of your hive. Varroa weakened bees are no match to determined hungry robbers. Ensure your hive is well treated using a combination of treatments for maximum effect.https://www.hiveworld.co.nz/product-category/hive-management/bee-health/varroa-treatments/