Where is the mechanical keyhole of the hotel credit card lock structure?

The mechanical keyhole of the hotel lock is on the front panel, that is, outside the door. There is a circle on the panel. You can see at a glance that what is not connected with the whole panel is embedded in the panel. If the disc is smooth, it should be sucked out with a sucker (a sucker is a doll that can be sucked on the glass). If there is a small hole in the middle of the CD, you should have an iron hook to hook the hole and then hook it out to see the mechanical key.