When filled, rollers, especially for very heavy loads. A two liter filled with sand is nigh on impossible to crush unless it gets pierced by some thing sharp on the outside.
Why not filled with water (filled all the way up, no air gap)? Water is pretty much incompressible.
WARNING & DISCLAIMER:
SELECT AND USE OUTDOORS AND SURVIVAL EQUIPMENT, SUPPLIES AND TECHNIQUES AT YOUR OWN RISK. Information posted
on this forum is not reviewed for accuracy and may not be reliable, use at your own risk. Please
review the full WARNING & DISCLAIMER about information on this
site.