I got an old utility cable spool, probably from the phone or power company, and turned it into a table - turns out this is pretty common, so I'm sharing the grommet/adapter I made to secure a patio umbrella in the central hole of the spool. This is easily resized to fit different spools and umbrellas. Works like a charm. I printed two of these, for the top and bottom holes of the spool table, it holds the umbrella perfectly, and allows the umbrella to be easily taken in and out of the table. Simple but functional.