We are the agents for Mettex Ratwall Ratblocker

As shown on the picture the rat blocker fits into the drain in a way as when the water runs down the drain the rat blocker lifts to allow the water to run freely.

Once the water has stopped running through the rat blocker goes back into a position where as no rodent can come back up the drain.

These are great devices and stop any rodent activity in the drainage systems to allow any access into your property.