Hi. Just a little used (pee) litter does the job. It's quite pungent, so the smell, for cats at least, carries a long way. It should not make much difference to neighboring cats. Although they might have a sniff out of curiosity.

We have always had a cat-flap, so our cats have had free access 24-7. They do get into a routine quite quickly.... But make sure it's your routine. Not theirs! Ours are allowed out day and night, but usually they come to bed at about 1am ish and sleep though till breakfast time. Although with the hot weather, they have been sleeping on the swing chair at the bottom of the garden at night. Much cooler for them. We have Foxes and Badgers as regular visitors to our garden (rural) and have had no problems with them for the last 15 years.

Ian.

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"Always turn and look when your cat gazes behind you with that intent look in her eyes. Some day there might actually be something there." - T.S. Eliot