There are several reasons why Coyote Rollers may not work for you and it may not be what you think.
There is a video that recently came to my attention about Rollers installed on a concrete wall where the Rollers are failing to keep a dog in.
What this video shows are the Coyote Rollers installed on the top of a concrete/block wall that could be 4-6" wide at the top. If a person is trying to keep a dog IN the yard with this type of fence. You MUST install the Rollers on the inside top of the wall (direction dog is coming from), not in the center of the concrete block.
If you've not seen the video, here it is:
As you can see, when the dog is able to gain a foothold on the side of the fence he's coming from (and also able to walk on the opposite side, just before he jumps off) they will be able to get over.
The Rollers work very simply. They MUST be used by the animal as leverage to get over a fence As long as the animal doesn't have another part of the fence, landscaping or a similar to aid their jump, the Rollers prevent a foothold. by spinning, when weight is applied. If you leave them a foothold, they will use it.
There are other examples that I've been provided as well. It is important to remember several things when deciding upon getting/using Rollers:
1) Your fence height is recommended to be 6ft tall for any instance (Coyotes, Dogs or Cats) anything shorter could be simply hopped over or climbed over.
2) You must carefully survey your yard/landscaping to ensure there are no objects that can be used as a boost to your pet/coyote for getting over and bypassing Rollers.
3) Proper installation is necessary to ensure the Rollers are spinning freely and provide complete coverage of the top of your fence.
4) The motivation of your pet or coyote may require secondary measures to keep them safe. Coyotes can dig under a fence, squeeze thru iron bars less than 3" wide, dogs and cats can climb chain link fencing like a ladder, their nails can dig into wood fences. There are a number of suggestions that I have that may help you with implementing secondary measures.
I WANT your pet to be safe - this is the reason I sell this product. I will tell you if I do not think they will work for you, for this reason alone. You must also take responsibility for proper installation, yard proofing and adding secondary measures as needed.
If you're not sure about your fence situation, please call me to ask. I want your pets to remain safely IN their yard.