Sandbag Tips

I recently bought the sandbag package sold by Ironmind. Any tips on how to seal the bags? I used duct tape on the yellow bags that I filled with 25 or 50 lbs of sand each. But the heavy blue bag I am not too sure about. When I only fill the bag with 100-150 lbs the bag is not even half full so there is a ton of room between the black strap and the sand. I tried bunching it up but it comes undone.

I use the draw string and pull it tight and bunch it up. I only use it for lift and carries, so it’s not a big deal. However, if you are doing other lifts, then it is a problem. I think you can use the strap and the drawstring to seal it shut.