I am trying to fit a new letterbox onto a wooden doorway. The door's 10 years old as is the letterbox and modern letterboxes seem to be a different size. The one I've bought is closest in size that I can find, but is still too big for the hole in the door. What's the best way of widening the hole by 15mm top and bottom? The bloke in the DIY shop said a wood rasp, but is there a better way?
Thanks! Appreciate any help that people can suggest.