This is a hook for safely hanging things by a looped thread or string. It is designed to hold the string securely so that it is unlikely to fall off even in the wind.  The hook can be screwed or nailed to a wall or overhang using a hole on either the back or the top.  The string slides into a narrow slot.  

I printed this to support an object outdoors in a sunny, hot environment.  I recommend printing it in a filament type that can support the environment in which it is going to be used.  The print shown is in ASA with 50% infill.