Frank's guests just need to get the Doorking 16120 default key and start letting themselves in.

Edit: undergrad shenanigans from ten years ago:

Our university student-run electronics lab had an issue: technically anyone with a student card was allowed on premises at any given time, but the department only gave us a small set of keys that we had to share with the rest of the student associations. Obviously we needed a solution.

We did some snooping and found that the request-to-exit button wire was running on a cable tray alongside all the other wiring and plumbing, as the lab was in the basement. We picked a suitably dark, inconspicuous spot and wired up a Raspberry Pi driving a transistor and in turn a relay which we then wired in parallel with that button. Users could then connect to the local lab wifi and then SSH into the device. Login shell was replaced with a script that pulsed the GPIO line for half a second and subsequently caused the door to open.

We never got caught and apparently all the evidence was destroyed when the building was renovated a few years later.