This model gives you the following parameters. They were everything found useful to be changeable on demand. If you have some feedback i would be glad to hear it :3. It's designed in FreeCAD and i used the hook in my home gardening to fixate the string on a steel frame behind by cucumbers :).

Parameters:

Hook Depth → Gap between front and back
Frontside Hook Height → How far below the top edge of the door the hook should be
Backside Hook Height → The piece of the hook which is on the backside to hold the hook in place
Hook Angle → Angle of the hook. How open/close should the hook be.
Hook Radius → Radius of the hook
Wall Thickness → How thick does the book should be
Extrude Width → How “wide” is the hook.