Why bother doing this on a database if you don't want to keep any of the information at all? If you goal is to make a list of patients assigned to beds, a simple spreadsheet would do the trick.
Unfortunately a spreadsheet has an appalling presentation, can be manipulated by curious people even when security has been applied and is restricitive in the advanced features I need to add. The file maker interface allows users to input the data in the right section with the right information, and importantly can't be manipulated by those who shouldn't. As well as this, I'm looking to add in a save function down the track, but I'm really interested in
1. How can I cap the records to 18 (each record represents a bed space)
2 How can I delete a record when a patient is discharged, so I can repopulate with new patient.
How about creating the 18 records you need, populating the fields that attribute to the "bed", that are not related to the patients and that never change.
Then restrict the Manage Security privileges for all users to allow no record creation.
Then write a script which clears all the fields that will change with a new patient, then make a button that runs this script, which would need to be deliberately pushed when a patient leaves, or a script trigger if more appropriate. The script will clear the fields and make ready for a new patient.