House fly trap

Trap for houseflies that can be screwed as a lid onto jam jars or preserving jars with a diameter of 77.5 mm. The many small holes allow the aroma of the attractant to disperse excellently, so that the trap works much more effectively than the common models for soda bottles.

To attract flies effectively, I use 5 to 6 teaspoons of fish meal for a 500 ml jar, which I fill about a third full with water.

I can highly recommend this anchovy fishmeal:
https://www.common-baits.com/BAITS/EINZELZUTATEN/Kleine-Mengen/Fisch-Muschel-Blutmehl/FISCHMEHL-SARDELLE-2-5Kg-65-Protein::2370.html

However, the stench of this bait can only be tolerated outdoors and is not suitable for indoors.

If you don't have a shelter outdoors, you should also print out the cap so that the jar doesn't overflow when it rains.