How to lock an inside door with round doorknobs turning both

I'd like to lock an inside building door, which I'm pretty sure is possible. The lock/doorknobs look like the pictures. The doorknobs can turn both clockwise and counterclockwise. How do I lock

PERFECT FOR PRIVACY with one-directional locking function and improved finish, these are ideal for bedroom and bathroom applications. To unlock,

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doors - How can I fix vintage glass doorknobs with loose glass-to

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