This is a pollen trap for Warré hives, designed by Marc Gatineau, a French commercial beekeeper, who kept 900 Warre hives for 35 years, now retired. The trap is available at:

It is a bit complicated construction. Still you can build it yourself.

The pollen grid can be pulled out to set or unset the pollen trap without removing the floor. Simply pull it out.

The pollen grid is pretty solid. A tin roof hinders debris from fallen into the pollen collected.

View from above. There is a drawer where the pollen falls into.

On the sides - left and right - there is a shutter.

The drawer can be drawn there.

In the front there are holes drilled, pieces of see-through hoses inserted. Incoming bees with pollen land onto the entrance board, outgoing traffic uses the hoses.

View from behind.

A floor board can be used for varroa monitoring.

View from the front into the pollen trap.

The construction of the trap is a little complicated with all the parts and stuff. But works well.