I did the 'Rat-Zapper' thread, and can't swear that it killed the rat, but the rat was gone 2-3 days after I put it out. It was basically the charging part of a disposable camera flash. I added a second capacitor (fried something on that board, so had a spare). Solder leads to the capacitors and attached those to some stainless steel wire I strung on insulators where I saw the rat on my porch. The second night He was back, but avoided the wired area. Several days later found the remains of a rat in the grass next door. Pretty sure it got zapped, but wasn't fatal. Only cost, was the batteries. Got the flash boards free from a pharmacy that does photo prints.