They are heavy duty bags filled with sand. They are used in the military to set up positions that are somewhat protected from enemy gunfire. The sand in the bags can actually stop bullets sometimes, so it's better than standing out in the open; plus these bags are easier to move than, say, a concrete or steel wall. Usually the bags are stacked on top of each other, a lot like bricks, so make a small wall that soldiers can hide behind.
To hit them really hard, as if hitting them with a sandbag
That depends on how much sand is in it. You should be more specific to what kind of sandbag it is.
revetment
Any person at any athletic level can benefit from the ulitmate sandbag. It is a good exercise for anyone who is able to handle picking up the sandbag. You do not have to be very ahletic to use one.
You can't play as the sandbag. (EDIT) Yes, by doing action replay.
Sandbag is not a playable character on Super Smash Bros. Brawl, it was made to be more of a punching bag.
0.5/inch
No. u can not play as sandbag in super smash bros brawl but u do get to use him as ant item.
Believe it or not there are websites that feature sandbag workout routines. One certified workout is at: www.ultimatesandbagroutine.com. Sandbags are a great way to lose weight.
sandbag
I have never heard of a sandbag workout. Your best bet would be to check with the local gym and see if they offer an instructional class to demonstrate how it works.
In one player matches the sandbag will appear time after time. In VS. mode go to options then go to items and turn sandbag on.