It is a natural building technique developed from historic military bunker construction techniques and temporary flood-control dike building methods. The technique requires very basic construction materials: sturdy sacks filled with organic material usually available on site.

To improve friction between bags and wall tensile strength barbed wire is usually placed between courses. Twine is also sometimes wrapped around the bags to tie one course to the next, to hold in-progress structures together and keep courses well-seated on barbed wire prongs. Rebar can be hammered...