Laying bags of sand.

Anything can be done right, incorrect or completely screwed up. That's what with sandbags to defend against flooding. If the bags are not stacked “with a tie”, even the wind blow can turn them over. The same is actual of bricks, wood...

Examples of a good arrangement “with a binding”.

Examples of bad arrangement, “without ties”

You should ask. Why aren't there any instructions? Badly stacked bags can prove futile work and human tragedy.