This particular MPD attachment is particularly aimed at those with amputee hands/forearms as a viable alternative to being able to turn the steering wheel without having hands.
Typically one ‘finger’ of the amputee hook will sit outside of the metal ring and the other ‘finger’ fits through the inside with both of the fingers coming together to secure an attachment to the ring.
This allows for an amputee the ability to turn the wheel using just their amputee hook and without requiring the other hand, which is similar in most other cases where just one hand is used because the other is using the hand controls.
Most paraplegics won’t find this device useful and it’s this group which hand controls and other pieces of steering wheel equipment are aimed at, however if you have one able hand and one amputee hand then this completely opens up the possibility of driving for you.
Availability for these types of items can certainly be limited so if your local disabled car shop doesn’t stock the Mobility Products and Design brand then it’s worth pointing out that MPS Monarch manufactures a similar hook grip for amputees which is attached to the steering wheel too.
Generally I would say that drivers don’t necessarily require turning aids such as knobs or tri-pin grips, although I’d certainly recommend them. On the other hand for amputees it’s definitely a necessity and someone which must be looked into.