I already draw this trap for a different thread and different application, so the secret is out, so may as well help everyone with the only perfect mouse trap you'll ever know of.
For rats or mice, it is built out of square metal tubing. Like aluminum extrusion from an old door. The bait is something that you are eating, drop a little bit into the trap after washing out the smell of the last mouse/rat. They would be suspicious of the smell of the last one. You'll rinse it after immersing the entire trap in a bucket of water without opening it to quickly and humanely kill the last mouse or rat if you don't release them.
The other bait is something out of a freshly opened packet, such as 2 minute noodles. A dry piece of noodle, uncooked, the size of a pea is perfect. This trap doesn't work by feeding the rodent, it works only on smell. You'd need to rebait the trap after a fortnight if there are no mice left in the house, because the bait would no longer smell.
The mouse only needs to enter the trap to investigate and it is finished. End of story. It doesn't need to nibble or chew or dance on a spring or anything like that. It is fast and it is final and it's the only trap you'll need to build, ever. I only built one and it has lasted pretty much forever. about 30 to 50 mice so far.. Because it is all metal it will last longer than I will.
for mice, the door sits on a AA battery or something else to prop it open. Sometimes it is a good idea to put something on each side of the trap to discourage the mouse from climbing on top of the trap first, which would set it off in false alarm. With a box each side, the mouse just goes inside first.
At the same time as you put in the bolts for legs, you could add a bolt to the roof so that you can change the balance of the trap later, by dropping nuts and washers onto the bolt.
I design and built this myself, different to other tilt traps because it uses straight pipe which makes it cheap and simple. It works perfectly time and time again.