Swivels are used to allow the operator to install fittings or hoses in such a manner to allow them to spin freely without binding or twisting. The two basic types of swivels are a right angle (or hose reel swivels) and inline swivels. Hose reel swivels are used to allow the operator to roll hose up on a drum without having to disconnect his feed line from the hose reel.
Inline swivels are commonly used on trigger guns and wands to prevent the hose from twisting and developing loops when the operator changes direction or spins around. When used between the gun and lance it allows the operator to rotate the lance freely to change the angle of spray without twisting of the gun which helps to reduce operator fatigue