A family of field mice moved into the house.  They are soooo tiny I wasn't sure what trap to use but this looked the lightest.  I caught the whole family within a few hours - even the babies. The secret as many have already said is keep in in their path and along the wall - I knew where they were coming from so it made that part easy.  Also, like already mentioned - just a dap of peanut butter - especially if trying to catch small mice.