Put vinegar, beer, wine, fruit, juice, or/and piece of fruit in bottle, put funnel in bottle. With a holed cork you can make one that hangs upside down, spout of funnel above level of liquid. Flies fly up to escape never find opening. You can buy decorative ones that don't look like bottles hanging all around, some sit on counter tops. They also catch house flys 'cause of bigger entry. Never tried beer as bait, seems like a waste of good beer, I ain't sharin with no fly. Wine is real good bait.