I've found EMT to be a good option for holding up string lights. The Maker Pipe Threaded Pipe Inserts gave me a better option for making the hook to wrap the wire around. I used 1" EMT and the 1/4-20 Insert With Lip. On top of the insert I added a rubber and metal washer, a brad hole tee nut, and a bolt with a wide head. I like to make my poles removable, so a piece of 1 1/4" EMT sunk in concrete makes a good sleeve. The last picture shows my old design, with a plastic cap with a drywall screw going through the cap into a drywall anchor. Not pretty but it's been holding out for 10 years. I like the new design much better!