To fill gaps in pine, you have a couple of effective options:

• For narrow to medium gaps, a water-based wood filler works well. It’s easy to apply, dries quickly, and cleans up easily with just soap and water.

• For larger or deeper gaps, consider using a two-part epoxy filler. This type of filler provides a strong, long-lasting repair and is ideal when a more durable solution is needed.

Both methods allow for sanding and finishing, making them suitable for both minor touch-ups and major floorboard repairs.