Our house before we moved in had been empty a while and so when we moved in within a couple of days we saw a little mouse!! we went straight out and bought some traps and these bait wedges. I put one by the door and one either side of the oven and within a couple of days we found the mouse outside that had eaten the bait and disposed of it. I have to say though its not the nicest way to kill them and sometimes they can eat the bait and then go and hide somewhere in the house or wall and then they can be quite a bad smell for some time. Quite cheap though and does work effectively.