Intermittent for starter use.

Per a technical site...

"A starter solenoid like the kind you see mounted on the fender well, or starter motor housing of some vehicles is used to bring current to a starter motor when the key is in the start position. This type is designed to pass as much as 400 amps. The length of time this high current passes through a solenoid like this is limited. The limited time is the key to their usefulness. These solenoids use a coil with only 3 to 4 ohms of resistance. If this type solenoid was turned on and left on continuously, it would destroy itself from heat due to the amount of current passing through the coil winding. These solenoid windings pass close to 6 amps when operating.

Continuous duty solenoid windings will draw less than 1 amp when operating. These solenoids will have approximately 15‐30 ohms of resistance across the coil winding. This allows the coil to run much cooler allowing it to pass well over 100amps continuously without failure.

Never replace a continuous duty solenoid with a regular starter solenoid. The starter solenoid will burn out in a very short period of time if used for “continuous duty.”

Often, depending on the manufacturer, intermittent and continuous units look the same and it's not possible to tell visually which it is. The parts counter guy won't know either unless he looks at the manufactures technical information. Online sites (Waytek, Del City, etc.) will, or should, have that info in the description. Or the auto parts will be selling it as a "starter " solenoid.

Using a 4 stud solenoid, with a 4th stud to ground the winding (as opposed to being a 3 stud grounded through the case) gives you an easy way to use a neutral safety switch. Just ground the solenoid through the NS switch to ground.