When refilling a small propane tank from a larger container (no lectures on disposable containers, please... only commercial, OPD tanks with proper hoses under discussion,) I need to bleed the receiving tank to relieve the pressure. This requires a 5-sided wrench that appears to be some industry secret. It's about a quarter inch (or so) in a quintagonal allen wrench.

What is the proper name for such a wrench?

Where can I buy one?

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