I started with drilling a hole in the side of my rain barrel to allow drainage, but I needed to put a screen over it to keep the bees out.  So instead, I made this bung so I could put a screen fitting in place instead.  Since then, I've made a screen fitting, a garden hose adapter, a ¾" NPT adapter, a ½" NTP adapter, and a 1" pool hose adapter.  It's been quite handy.  There's also a nipple in the 3mf to go from female to male, but I probably should have put a hex in the middle to gip it with cause it hurts your hand when you try to put it in.

Made from PETG.  Message me for the fusion 360 file.