We're in the middle of the sanding / filling / sealing process for an old traditional boarded floor (i.e. not interlocking planks) and are trying to work out the best way to fill in some of the many gaps between boards. For the wider ones we've inserted some thin beading, but there are others that are still very wide but too narrow for that. I've heard recommended mixing up our sawdust with the varnish and inserting that - but frankly that sounds like a messy nightmare ! There don't seem to be any commercial products on B&Q's shelves (most of the wood fillers specify 'not for between floorboards') but unhelpfully don't recommend anything else. Any ideas ? Many thanks