Jacks come in two basic types bottle (from left to right - jacks 1 & 2) and scissors jacks (jacks 3 and 4)
They are raised using either mechanical force (jacks 2 & 3) or hydraulic pressure (jacks 1 & 4). Some mechanical jacks may have a switch to raise or lower the jack. Scissors jacks have a low profile which means they can get under a pup with low ground clearance Hydraulic jacks have a bolt that is tightened to raise the jack and loosed to lower the jack. They are faster than scissors jack but do require more maintenance.
In selecting a jack make sure its :
1. weight rating is adequate
2. It can fit under the frame with a punctured tire
3. It can raise the PUP high enough to replace the tire (Note if you have to add boards to raise the PUP up, then the jack and boards need to fit under the PUP when the tire is flat.