How far apart would you use these, if you have a big area, like a 60x72 ft barn? Would one behind and one in front be enough?

We generally recommend hanging the traps at least 20-30 feet apart, but it also depends on how many flies you have. You can start with two traps, but you may want to consider using more if they fill up quickly. Please contact us at info@rescue.com if you have any other questions.