The Trombone Sprayer is a simple type sprayer also called syringe or slide-action sprayer. The pump cylinder and plunger are the parts of the spray lance. The pump is double action, so spray is possible both in forward and backward strokes. The part of the cylinder surrounding the piston rod/pipe acts as a temporary storage chamber in which the spray passes through the hole in the piston in the piston wall. On the next backward stroke the liquid trapped in this storage chamber is forced out of the hole and finally through the nozzle. A knapsack plastic container of 10 to 20 liter capacity is used to contain the chemical. A PVC hose pipe fitted with a strainer/filter is used as a suction pipe to pump in the spray chemicals into the trombone from the knapsack container. The sprayer produces a fine spray and fitted with a standard hollow-cone nozzle.

The Semi-automatic Trombone Sprayer has a pressure chamber (looks like a plastic ball) just after the Lance Grip. This pressure chamber reserves some pressurized spray contents, which passes through the nozzle at the time of pumping intervals. The pumping is also easier than normal trombone sprayer and the spray will not stop when pumping is stopped.