In Reply to: Actually, I've just thought up a very posted by Limerick on Wednesday, 13. February 2008 at 08:35 Bali Time:
the hotel has coloured plastic disks which guests sign in for on the same day they want a sun lounge.
Eg Orange disc = 11 am
Purple disc = 9am
Maximum time one can use disc is 2 hours
Attach the disk to the sun lounge to signify to other guests it's in use.