I used these stands on a project recently, supporting part of a Toyota Camry during a strut change (see the review posting about the Monroe QuickStrut replacement). The stands are sturdy, with welded steel bases and thick, cast iron posts. The adjustment range is from 11 1/2 to 16 3/8 inches. The 11 1/2 minimum means that most cars will need to be jacked up only enough to get the tire(s) off the ground before the jack stand can be positioned under the car.
How I Use Jack Stands
I jack the car up, put the stand under at a sturdy location, and let the jack down so that the car rests on the stand. I leave the jack up just below the stand as an added safety measure. It is not recommended to use the jack itself as a substitute for a jack stand. In other words, it's not a good idea to leave the car resting on the jack itself.
The key to using these jacks is that they should be placed on a concrete floor. If you have dirt, gravel, or asphalt, the legs are likely to dig in because they do not have a flare out on the base. The legs are shaped like angle iron with just a small amount of metal transferring the weight to the ground.
Included is a "safety tab" that you are to bend in after assembling the post to the base so that the post cannot slip out or be raised beyond a safe height.
And, of course, use the stands on a level floor so the car won't shift and fall off the stands. (You are putting blocks under the wheels that stay on the ground, aren't you?)
Harbor Freight often has "Super Coupons" for these jack stands, bringing the price down to a reasonable point and making good value for the money.