The neighbours' cats were hunting for my goldfish. These felonious felines would lie with chest on the edge of the pond, both front paws in the water, claws extended, waiting to snag a passing fish, just like a poacher tickling for trout or salmon.
A single strip of the spikes around the water's edge (I've posted a pic) has persuaded both of the cats that the discomfort is just not worth the sport. I watched as each one tested the strip with a tentative paw, put more weight on it and then decided, 'No, I'll look elsewhere today,' and pretended they had never really been interested in the pond anyway.
The spikes come as a triple width strip that can be separated into three thin strips - three times as long for the same outlay. However this is useful because the thinner strip is the ideal width for fitting along the top of a feathered-edge garden fence - another avenue now closed to the cats, and also the squirrels. The wider triple strips I have fitted on the top of some brick wall to try to discourage intruders from climbing over.
Each strip is 450mm long and 15mm wide, ie 45mm for the triple strip. Fixing holes are at about 110mm centres. The middle strip has only four fixing holes because they are offset slightly compared with the outer strips, and where the centre hole might have been is actually a spike. The spikes are cones 15mm high, about 7mm diameter at the base, and 1mm diameter at the tip.
There is also a discreet and yet reasonably robust plastic warning sign enclosed in each box. But the cats and squirrels cannot read, so it will not deter them from trying. And the spikes are not so dangerous as to cause serious injury to a burglar, unlike broken glass cemented on top of a wall. So I expect that with warning sign and only plastic spikes, we should be safe from any type of vengeful personal injury prosecution by a discomforted and disappointed felon.
A good investment.