What does sandbagging mean?

Beating sandbags, a traditional Chinese folk children's game.

A square cloth bag, with six sides, is three-dimensional. Containing corn, sorghum, wheat, beans or fine sand grains, generally homemade, side length of about 5cm to 10cm. Homemade note, sewing the mouth at the end of the time to leave a small hole (is left out to put the particles), and then turn the whole thing over (put the filler in after sewing), so that you can not see any stitching on the outside.