Self Check-in when the office is closed

[CodyClassB]

I was in Mammoth Lakes last weekend and noticed the sign at the RV park "Unregistered guests, pick up the yellow envelop and check in the next morning at 9:00am". How popular is self check-in at RV Parks?

The next time I arrive late after the office is closed, even if there are no "self check-in" sign, can I just pick a spot and stay overnight. Pay in the morning when the office opens?

thanks

[GordonThree]

Pretty common at Michigan State Parks ... The ranger at the gate has been replaced by a yellow phone and some distant call center