I use what tvov shows on his post. My 5er is in storage for the winter. For the last two or three years I have used that and I check the trailer every so often. I put two of them behind the rear wheels and the wheel covers hide them. After the first year of mice eating the blocks, I have found that there isn't mouse activity around the trailer. Knock on my head. I did find one mouse in the toilet. I think he was trying to drink the anti-freeze or wanted to take a swim in the pink stuff. I have no idea how it got into the toilet tho'.