My mother drops a penny in a ziplock bag the adds water. Zips it up and hangs one just outside of each entrance to the house. Works very well to keep flies away from doors therefore also from flying through when they are open.
I would like to know how to get rid those pesty little sink/drain flies. I've tried baking soda and vinegar, drain cleaners and put plastic over the drains.
Here's some ideas: https://www.hometalk.com/search/posts?filter=kill%20flies
I suck them up with my vacuum let it run a little and they die
try some of these tips: https://www.craftylittlegnome.com/flies-house-suddenly/
Are you dealing with fruit flies or regular black flies?
Dynatrap. it's marketed for mosquitos but has gotten rid of the flies.
My mother drops a penny in a ziplock bag the adds water. Zips it up and hangs one just outside of each entrance to the house. Works very well to keep flies away from doors therefore also from flying through when they are open.