We use these for chipmunks.  Place some seeds tightly in the clasp.  Place somewhere that birds or other animals will not get at it, you could build a tiny chicken-wire box for it to sit inside of.  Make sure you tie it down, if your pest is caught but not instantly killed you don't want him dragging this away.  With that said, it is very very powerful, unless he steps on it from the wrong direction, it will be a clean kill.  Watch those fingers.