While partially true, you are NOT supposed to jerk on it. They're called snatch straps and the way they work is that you take up the slack and then slowly start stretching it by driving forward. The potential energy built up within the strap by the elastic properties will reach a limit and then turn into kinetic energy, pulling the stuck vehicle.
The elastic fibers in them WEAR OUT and most of the better quality snatch straps have a color property built in, so that when that color shows up, you should stop using that strap immediately because it has been overstretched and will not function properly. I have two straps that i keep (one in vehicle) for uses other than vehicle recovery.
It is still a good practice with these straps to weigh down the strap with a heavy blanket or something so should it brake something off where it is attached, it doesn't turn the d-ring shackle into a projectile.
And for what its worth, I have 4 and have owned 6. I always carry a 2"x20' and a 3"x30' strap with me, along with about 6 shackles (4 larger, 2 smaller). I have towed a UPS Freight truck (the straight body, not tractor/trailer setup) out of a ditch when he slid into snow and the guy was impressed and glad that he didn't have to call a tow truck. Gave me a $5 even though I refused and said to buy myself a beer. Very nice guy.
Taken from: http://www.arb.com.au/getting-starte..._Equipment.php
Here's another site that actually shows how to connect two straps together without a d-ring shackle: http://www.racq.com.au/motoring/cars.../snatch_strapsNOTE: Excessive speed and continual jerking action whilst using a snatch strap may result in damage to the recovery point, chassis and drive line of both vehicles. Where proper use of the snatch strap is not successful, an appropriate sized recovery winch should be used.​
Anyways, glad you had fun with it, they're amazing tools when used properly!The recovery vehicle steadily accelerates forward at about 10 –12kph – a big ‘run and jerk’ shouldn’t be used. Steady momentum and strap elasticity does the job. As the slack in the strap just takes up, the stricken vehicle’s driver also attempts to drive out of the bog. Be smooth, avoid wheel spin and don’t use excessive speed or continual jerking.
eta: I have used the yellow straps and the grey straps which I believe are pro-comp. They all work the same, but I know the yellow straps have the built in red elastic which shows when the strap has reached its limit.