Deer have horrible vision - 20/100! They have a 360 degree view horizontally, but they cannot gauge what is directly in front of them, or over their heads after 7' feet high. If gardeners don't let deer know that a fence enclosure is ahead, deer may run right into it (especially if they are being chased by a predatory animal like a coyote or wolf).
Because deer vision is so poor, Deerbusters recommends adding white warning banners to the deer fence to let white-tailed deer know that a structure is near. Whitetails have trouble seeing the black color of the fence mesh; but they can easily detect the white color on the deer warning banners. We recommend that you tie one white warning banner on the fence for every 10 feet at a height of 4 feet. Avoid adding warning banners to the top of the fence -this allows the deer to gauge how high they need to jump to get to your garden.
Deer warning banners come 50 to a pack, at 1 inch x 24 inches.