MartinH

Going back into the distant past and an engineering aprenticeship - the file only cuts on the forward stroke but as long as there is no pressure on the file during the backstroke it won't do much harm - I've not seen many fellow engineers lift the file clear during the backstroke - unless it's the last few finishing cuts and the extra time/care is warranted. Sharpening any tool follows the same principle - little and often, don't let it get too blunt in the first place!

The much maligned grey squirrel does have its uses - it is quite tasty! A good way of exacting revenge for the damage it can do with its feeding habits!!