When blocking vermin access, make sure you don't also block egress!

I did that very successfully for one of my cutomers, and contained 2 trapshy rats in their house. It was four days, they told me, and four VERY long nights, before they starved enough to finally have to take the bait.
They were using a hedge to give them access to the roofspace. The garden was full of uncollected ripe fruit, and in that salubrious part of town, every house has a wastemaster.
To explain the plumbing route, the kitchen waste goes into the toilet waste just outside the house. As far as rats are concerned, it's a good way in. If you find your drain grille displaced, Ratty did it. If you do the man thing and leave the pan lid up and find unexplained water on the toilet floor, you've had a visitor.
I don't think they can cope with a lid-down toilet, but I don't think I would put money on a modern lightweight lid. You'd know, though, because, they wouldn't be able to get back out again. I think.
   
Rats are athletic and smart. They can climb a 6inch vertical plastic pipe by using 'chimney' technique, they can jump a couple of feet, and they can climb VERY well. They are also smart and strong enough to use a cat-door, and some have been known to back a nervous cat down. A full-grown rat is an impressive animal. and it takes a terrier to tackle one.
To 'tune' snap traps, make sure there is no 'wire edge' or other tiny snags on the part that holds the killing stirrup down, just where it passes under the trigger/baitholder. You can also lubricate it with cooking oil, but some oils go sticky after a while, so you have to keep reoiling. When loaded, they work most humanely when they're placed in a recess so that the bait is the most accessible part. This makes them pull the best way.

This should qualify me for jOhn's 'talk too much' thread. Thinking of jOhn's post above, I wonder if Rentokil do a morris-dancer trap?