How can I pin code lock my phone without advertisements, or popup screens?

Ive' searched for days to find a pin code lock app. They either put adds on my phone, or they access files that are not necessary for a simple app. I've searched in both free and paid apps for my android phone, and have not yet found one that ONLY locks my phone and shows the time without unlocking. I can do without the time if that isn't doable.

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