axle stand is a device that securely supports the axle at one corner
of a vehicle, so that a pair of axle stands enables a person to
work safely underneath. Unlike a trolley jack, which has seals that
can fail (with potentially disastrous consequences for anyone underneath),
axle stands are held in place by either pegs or ratchets. Also they
allow the weight of the vehicle to be spread evenly over two points.
Stands should be marked with a Safe Working Load (SWL). The larger
the number, the better. As each stand supports only corner of the
vehicle, a one-ton rating is more than enough for most applications.
However, be aware that some manufacturers give a "per pair" rating.
Another important factor is the size and shape of the saddle that
supports the axle. A wide top with a cupped design is preferable,
as it gives more stability. However, the cup shouldn't be so deep
that its upper edges can damage the underside of the vehicle. An
iron saddle is less likely to cause damage than a steel one.
Ratchet stands are easier to use than peg types and afford a wider
range of height settings. Other factors to look for include feet
on each leg to spread the load and prevent the stand digging into
the floor. As far as height goes, an 11-inch (280 cm) maximum is
fine for the average car; owners of 4x4s should add an extra 4 inches
(100 cm) to this.