In article ,
Grandpa Chuck wrote:

We tried almost everything recommended to get our two cats to use
their litter pans and they do a pretty good job of it. However,
regardless of how often we clean and/or change the litter they still
go to the basement and **** on the floor up against the wall and the
riser for the bottom step.

The last thing we tried was washing the area thoroughly with citrus
based cleaner and then laying a towel there soaked in the solution for
about two days. Then we took three layers of newspaper and laid them
on the floor and part way up the wall and up the riser. We put a 50#
weight on it so they could not move it. By the next morning the
newspapers were stained with cat urine.

There has to be a definitive answer that will convince them to go to
their litter pans every time.

Anyone have any suggestions that do not involve harming the cats?

Don't know whether this has been suggested, and I'm not going to read
all the posts to find out -- but I don't think anyone suggested it on
the first go-round: Aluminum foil. They still might find another place
to pee outside the box, but it won't be there.