h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If the neighbourhood cats are using your garden as a lavatory, fill some bottles with water and leave them lying around in the garden.

They can be glass or plastic, as long as they’re clear.

I think I know why cats don’t like them, but it’s only a guess. If you get your head down to cat’s eye level and move it from side to side, anything seen through the water moves illogically and might, I think, look like something living and possibly menacing. Anyway, whatever the reason, these bottles do the job.

They’re also fairly unobtrusive. On the other hand, if you want to show off your garden or you’ve invited people round for drinks on the patio it’s the work of a moment to bring the bottles in and hide them in a cupboard – far quicker and far more enjoyable than scraping cat excrement off the soles of your shoes.