You can use rancid fats to make soap, but I prefer to use it oiling my shovels or other tools. I use it on a rag and oil the wooden handles and metal ends to defeat rust and keep the handles splinter free for next year. Or get fancy and get a bucket of sand and add the oil to it. Then shove the shovel in and out and it is well oiled. I don't make 100% olive oil soap as it took forever to trace the one time I did. Try using a recipe that mixes oils for faster tracing.