I got some sheets of sandpaper 230mmx280mm (a little wider and shorter than A4) and wanted a handy holder to turn strips of it into sanding blocks to make jobs easier. This is what I came up with.It is designed to grip sheets of sandpaper cut to 40mm wide by just over 200mm long, but with the files included it should be easy to re-design to your needs.Print off a part and fit the hole with one M4 bolt, two washers and a wing nut. Slice your sandpaper into appropriately-sized strips from the back and do any tearing necessary. Wrap a slice of sandpaper around the holder and tuck the ends into the gap, then tighten up the wing nut while holding the bolt fixed. Sand away!