Back in my 2 wheel drive days I would put 4 semitruck brake drums in the back. Nice and heavy and no chance of sand getting everywhere, not to mention they are free.

 

I hope they were strapped down! Same with anyone else putting anything heavy in the bed... Remember these can be like cannonballs coming in through your back windows if you get in an accident. Especially dangerous if you have children in the back seat!

 

Exactly...Several years ago I lost a friend when the driver of a delivery truck blew a stop sign. He T-Boned it. A shortened RailRoad Tie became airborne from his bed penetrating the Cab, Killing him.

 

That is why I wanted mine 'contained', so they didn't become frozen blocks of flying death. I put mine in when they are warm, they conform into their spot, freeze and stay put all winter.

 

Anything you use for weight is going to become a projectile during a collision or rollover. If you rearend something substantial, that weight is going to come through the back window and a normally survivable incident now becomes a funeral(s). In the 70's I used snow for weight ... filled the entire box on my '68 Mercury. Don't think I'd do that with my aluminum box tho. In my '91 Dodge diesel I bolted heavy steel into the frame with a lot of bolts. That old clunker still gets 31 mpg. Remember, it's all fun and games until someone loses an eye!