This is an S-hook that work great for stringing Christmas lights onto your gutters. I placed them about every 2-3 feet. I used them on common plastic gutters from home improvement stores like Menards or Fleet Farm that are flat or have ridges on the interior side.

I made these on a Replicator 2X in ABS. Not sure how PLA will react. I found that a triple wall without any fill worked very well and performed the same as a double wall with 100% infill.