I use these:
Tomcat trap

I have them in open areas, along the base of house and garage.
The structure of the bait blocks (they center mount on metal pegs) makes it almost impossible for a rat to do anything but gnaw at it.
Window on top means you can see if the bait is disappearing without opening.
2 thumbs up.

1970 T120R - 'Anton'
1970 Commando - 'Bruno'
1967 T120R - 'Caesar'
1972 Commando - 'Big Red'