a_older_gent

I was at a knife show recently and saw some beatiful knives made from files. The name of the file (nickleson) was visible in back of the handle and you could see the teeth of the file on the unground parts of the knife. In talking with the salesman (he did not make the knife) he informed me you would have to soften the steel (annealing I think) then grind out the blade the re_harden the blade. This sounds simple but when researching it is confusing to me. 1st Question how would you anneal the file? 2nd What is the correct method to reharden the blade with out making it to brittle? Thank you for explaing this to me in laymen terms.