Wide gaps between the floor boards can let cold air or dust come up from underneath the house.
Filling the Gaps
Applying the paste between the boards - using a mix of the finer sanding dust and a clear resin substance. As the sanding dust is from your floorboards the paste is the same colour as your floor.
Sanding Off
Once dry, the residue of the filler is sanded off to a smooth finish.
A Gap Filled Floor
The completed gap filled floor looks tidy and uniform.