I have two cutters. I have the one
@Zing has but the wire tended to move a little and make a wave in the soap. So I decided to go with an all metal cutter. Best decision I made since I started soaping. I got the single bar cutter from nurture soap and I love. It is built so well and the handle is weighted just right that it almost makes the cut for you. It is powder coated and there's no exposed metal to rust on you. I wanted the multiple bar cutter but they were out so I got the single. It is a little pricey and I live close enough to pick it up from the store so I didn't pay for shipping but I think the shipping is free. It is $158 but if you can afford it, I highly recommend it.
The only down side is that it will only hold a 9 inch loaf by itself. If you have bigger molds than that, you will need to buy the extension.
https://nurturesoap.com/products/single-soap-cutter