The ports of the angle valve ( Inlet and outlet) are oriented at an angle 90 deg.

The area where a valve closes in the combustion chamber of a four-stroke engine is called the valve seat. During a valve job, this seat is ground at a set angle, usually 45 degrees, for a good seal. In a three-angle valve job, additional angles are ground into each side of the seat angle to ease the transition and improve flow.

where the process require the fluide to be leave at right angleto the direction in which it enters at that time we use angle valve

By shutting off the water supply prior to this valve of course

To regulate the flow of a liquid or gas.