Very OLD design. I think this design dates back to the 1800's. The new plastic traps and the Tomcat brand knock-offs, etc. aren't this good. It has a VERY strong spring capable of breaking adult human fingers. There's no safety features on this so you MUST place it where kids and pets can't get to it. Once it's set, it has a hair trigger so you need a steady hand and calm nerves. I set one of these in my garage and was just getting ready to place it when a mosquito hit the bug zapper and my life flashed before my eyes. They're pretty reliable for holding the rat. Whether the rat dies or not depends on what position it was in when the trap actuated. My first rat was dead as a stone from the bar hitting the back of its neck. Another rat had its pelvis crushed and was trapped but alive forcing me to behead it for a quick, humane kill. So nothing's perfect but these traps are strong and USUALLY kill immediately. They're more durable than the plastic ones. The only thing that might work as well is the electric one but those are expensive. Around forty dollars for ONE at the time of this writing.