We have a summer cottage from the 50s with some damaged sills in a few places. I don't see the replacement itself as a problem, but I'm not quite sure of the best solution to get a replacement in the right dimension for the new sill.
The old one is 65x170 and those aren't available in the hardware store. Should I make my own sill based on 45x70 where I cut off 5mm and glue and screw together 4 pieces, or use something like a 45x170 on top of a 20x170? Or is it best to contact someone who can cut a custom dimension?