Glasses don't easily allow for pencils behind the ear, and I wanted to fix this challenge. After seeing amazing 5-panel hats online, then being shocked by the price tag, I decided to customize my own.
This clip is created specifically for my hat's measurements, but can easily be customized and adjusted to fit other hats. For the left side (shout out to all the Lefties!) of the hat, this clip has clearance on the back to guide the pencil into the holder, and a clip on the inside to fit over the lip of fabric inside the hat.
Special thanks to brendandawes for the Ticonderoga clip, which was used as the actual pencil holder on this hat clip. Check out this amazing book clip that inspired this hat clip: https://www.thingiverse.com/thing:12791