The message
from "Amateur Gardener" contains
these words:

I've just become aware of rats running up the bird table to get
the bread. The rats seem to live under the shed.

I've put down poison bait on tobacco tin lids under the shed,
and this gets taken, but so do the tin lids!

Not big enough. You need:

some lengths of plastic drainpipe - say, of two feet. Starting with a
longer length, cut them out like this:
__________________________________________________ ________
|/ \/ \/ \/|
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯
_ __ _
|/ Discard \/ Keep - turn ( )
_______ ________ ^
/ -- \ L_ cut
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
__
Cut the bottoms of the \/ wedge-shaped bits of tube you have left over,
so you can slip them over the pipes.

Cut holes in the middle of pipes, so you can put at least a wineglass of
poison in - or a tomato purée tin full.

Slip cut ring over hole.

Place pipes beside vertical surfaces - rats (and mice) tend to run along
the bases of walls, etc. Yhey like tubes like drainpipe to run
through...

"Ohhh! Dinner!"

Don't forget to check them and to keep them topped-up - rat poison isn't
immediate, and it may well take a week or more to have a permanent
effect.

Remember too, that hedgehogs and animals you might not want to
annihilate will eat rat poison, hence the pipes. TAAAW, it is illegal to
leave open trays of ratpoison about willy-nilly.

The rats ignore the spring traps and the squirrel trap (big square
wire frame)

Bait them with chocolate.

How do I get rid of them and also know that I've got rid of them?

They're only 10 foot from the kitchen door which I now keep
resolutely closed.

More poison. If they continue to turn up,

--
Tony
http://www.users.zetnet.co.uk/hi-fi/