dkwflight

Hi I am trying to teach myself how to make shoes. I watched all the vids I have found. Preparing the insole for stitching is a problem for me. Some have mentioned a special knife, a welting knife. I bought an old knife identified as a welting knife but it does not seem to work for me. It seems to be a groover with a cutting edge above/ next to the groove curl. Does anybody here know where to buy the proper knife. Thanks Dennis