This drops into a socket and holds a hook for screwing in or out. Originally designed for a 12mm socket, the 15mm version is just a 125% scale-up. Other sizes for different hooks can be scaled (metric or not), or just add some tape. It is strong, especially in PETG, so be careful with power drivers.
The detent helps to keep it from falling out of the socket, but it needs a little more development, or just some dry rubber cement.
When starting a new hook, you have to go straight in. Bent hooks (sideways) are very difficult to work with.
The author marked this model as their own original creation.