I have used these in my backyard for years. It's amazingly effective at trapping wasps. I either hang it from a tree branch or put it away from where we are eating.
Just fill the Wasp Trap with sweet liquid, and the wasps will immediately be attracted to it. They climb through the opening in the bottom of the Wasp Catcher, crawl inside and become trapped while they feast on sugar water. You are left to eat your meal in peace, with a wasp free table.