I would like to make a thorn covered surface to repell small rodents from traversing it - any ideas?

nothing seems to deter squirrels, but I noticed they can be kept somewhat at bay with thorns from blackberrys or rose bushes. but as the canes dry the thorns fall off and they can be moved out of the way

I believe you can get a spikey material which they use lots at airports. They don't wants birds hanging around so they put it on anywhere a bird can land. Not sure how well it may work on squirrels but maybe it's worth a try? What about using grease? or maybe something really sticky?
The spiky material is called bird control spikes. I see some spike strips on Ebay's Buy It Now (including shipping) for $6.31 for the first foot and + %2.68 per additional (plastic) or for $5.09 per foot (steel)
BioZone8 years ago
I had some bird feeders in MN that the squirrels wouldn't leave alone and after trying several different barriers finally went with an electric fence. The nice thing about this was I could turn it off so I didn't get pricked/shocked and it's surprisingly low profile. For additional fun you can also wire it into a light switch inside the house and wait until they're on the feeders, they seem to learn after a while. If you're committed to the spikes I recommend thumbtacks and some epoxy, you can stick them anywhere you like and the surface area on the back is enough to ensure that it won't come unglued.
Gray squirrels are not especially smart in general. But when it comes to getting food, they are incredibly persistent and will learn (and remember) how to circumvent almost any barrier. They can also leap considerable distances (as much as 10 feet from the right takeoff) and drop even farther.

You might want to create a new question in which you explain exactly what it is you want to stop squirrels from doing and exactly how the yard is arranged. It may be that you could repel them with hot peppers, chicken wire, or something else.

If preventing them from walking is actually your goal, try this. Spread a thin layer of carpenter's glue (or other cheap waterproof glue) across a sheet of plywood (wider than they can jump and away from nearby trees, of course). Empty a box of flat-headed tacks onto the board and flip them upright (either by hand or by waving a large magnet over the back.)