A sturdy wall hook. 
Designed to serve as a holder for roof bike racks. I'm not the type to drive around with them on my car all year round, and I don't want to trip over them in the garage. It doesn't get in the way on the wall, and I always have them within reach. It fits Thule, but also cheaper copies. I tried printing a version with a bottom and top shell, but I also experimented with exposed honeycomb filling. Both versions are strong enough, so it depends on your preferences.