Jet (or Wave) soldering is similar to wave in that it’s uni-directional and provides the same benefits as wave. Its smallest solder diameter is 4mm, it requires minimal maintenance, and it is fairly low cost. The solder ball jet nozzle type you use will depend on the make-up of the board and the location of SMDs on that board.
For instance, a fairly large row of connectors/leads not in close proximity to SMD components could use a wide solder ball jet nozzle to swipe (or wave) the entire row at once. A small area closed situated to an SMD would require a very small solder ball jet nozzle to avoid disturbing the surface mount device.
Solder ball jet nozzles attack the board at about the same angle (7) as a Wave machine, and can deliver a high volume of solder using a tapered tip which guides solder roll-off in one direction returning unused solder back to the pot from its trailing edge. In this scenario, the direction of travel (board or nozzle) is very important.
Solder ball jet nozzles are long-lasting and usually cost only a few hundred dollars. Some boards can benefit from a custom solder ball jet nozzle to solder an area as quickly as possible in a dip or drag process, or even a min-wave.