There are Trimming Potentiometer (aka trimmers) - pots designed for "set and forget" applications. They are used for "trimming" the value of a resistor, and are commonly used for calibrating instruments, setting the bias current on power amplifiers, and a host of other areas where a circuit cannot be relied upon to give an exact gain, output voltage, or current. Naturally, a normal panel pot can be used, but these are very much bigger, and any calibration or setup control should not be made available for everyone to fiddle with as they please.

This is a very small sample of those available. The first and fourth are multi-turn types, and these should be used when a very precise setting is required. Because they are sealed, they are relatively immune from contamination, and for all but the most trivial application, should be used instead of the open types.Trimming Potentiometer(as shown) are generally available as vertical or horizontal - the choice is usually made based on ease of adjustment of the final circuit.